Silence gcc 7's fall-through warnings in `switch' blocks.

Instead of an intentionally missing `break' statement there must be a
comment line containing `fall through' (and nothing else) right before the
next `case' statement.

See

  https://stackoverflow.com/questions/45129741/gcc-7-wimplicit-fallthrough-warnings-and-portable-way-to-clear-them

src/gzip/infblock.c

@@ -335,6 +335,7 @@ int r )
       }
       ZFREE(z, s->sub.trees.blens);
       s->mode = CODES;
+      /* fall through */
     case CODES:
       UPDATE
       if ((r = inflate_codes(s, z, r)) != Z_STREAM_END)
@@ -351,11 +352,13 @@ int r )
         break;
       }
       s->mode = DRY;
+      /* fall through */
     case DRY:
       FLUSH
       if (s->read != s->write)
         LEAVE
       s->mode = DONE;
+      /* fall through */
     case DONE:
       r = Z_STREAM_END;
       LEAVE

src/gzip/infcodes.c

@@ -117,6 +117,7 @@ int r )
       c->sub.code.need = c->lbits;
       c->sub.code.tree = c->ltree;
       c->mode = LEN;
+      /* fall through */
     case LEN:           /* i: get length/literal/eob next */
       j = c->sub.code.need;
       NEEDBITS(j)
@@ -164,6 +165,7 @@ int r )
       c->sub.code.tree = c->dtree;
       Tracevv((stderr, "inflate:         length %u\n", c->len));
       c->mode = DIST;
+      /* fall through */
     case DIST:          /* i: get distance next */
       j = c->sub.code.need;
       NEEDBITS(j)
@@ -194,6 +196,7 @@ int r )
       DUMPBITS(j)
       Tracevv((stderr, "inflate:         distance %u\n", c->sub.copy.dist));
       c->mode = COPY;
+      /* fall through */
     case COPY:          /* o: copying bytes in window, waiting for space */
       f = q - c->sub.copy.dist;
       while (f < s->window)             /* modulo window size-"while" instead */
@@ -225,6 +228,7 @@ int r )
       if (s->read != s->write)
         LEAVE
       c->mode = END;
+      /* fall through */
     case END:
       r = Z_STREAM_END;
       LEAVE

src/gzip/inflate.c

@@ -174,6 +174,7 @@ int f )
         break;
       }
       z->state->mode = FLAG;
+      /* fall through */
     case FLAG:
       NEEDBYTE
       b = NEXTBYTE;
@@ -191,18 +192,22 @@ int f )
         break;
       }
       z->state->mode = DICT4;
+      /* fall through */
     case DICT4:
       NEEDBYTE
       z->state->sub.check.need = (uLong)NEXTBYTE << 24;
       z->state->mode = DICT3;
+      /* fall through */
     case DICT3:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE << 16;
       z->state->mode = DICT2;
+      /* fall through */
     case DICT2:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE << 8;
       z->state->mode = DICT1;
+      /* fall through */
     case DICT1:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE;
@@ -234,18 +239,22 @@ int f )
         break;
       }
       z->state->mode = CHECK4;
+      /* fall through */
     case CHECK4:
       NEEDBYTE
       z->state->sub.check.need = (uLong)NEXTBYTE << 24;
       z->state->mode = CHECK3;
+      /* fall through */
     case CHECK3:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE << 16;
       z->state->mode = CHECK2;
+      /* fall through */
     case CHECK2:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE << 8;
       z->state->mode = CHECK1;
+      /* fall through */
     case CHECK1:
       NEEDBYTE
       z->state->sub.check.need += (uLong)NEXTBYTE;
@@ -259,6 +268,7 @@ int f )
       }
       Tracev((stderr, "inflate: zlib check ok\n"));
       z->state->mode = DONE;
+      /* fall through */
     case DONE:
       return Z_STREAM_END;
     case BAD:

src/psaux/afmparse.c

@@ -953,7 +953,8 @@
         error = afm_parse_kern_data( parser );
         if ( error )
           goto Fail;
-        /* fall through since we only support kern data */
+        /* we only support kern data, so ... */
+        /* fall through                      */
 
       case AFM_TOKEN_ENDFONTMETRICS:
         return FT_Err_Ok;

src/sfnt/sfdriver.c

@@ -375,47 +375,61 @@
       {
       case 15:
         k4 ^= (FT_UInt32)tail[14] << 16;
+        /* fall through */
       case 14:
         k4 ^= (FT_UInt32)tail[13] << 8;
+        /* fall through */
       case 13:
         k4 ^= (FT_UInt32)tail[12];
         k4 *= c4;
         k4  = ROTL32( k4, 18 );
         k4 *= c1;
         h4 ^= k4;
+        /* fall through */
 
       case 12:
         k3 ^= (FT_UInt32)tail[11] << 24;
+        /* fall through */
       case 11:
         k3 ^= (FT_UInt32)tail[10] << 16;
+        /* fall through */
       case 10:
         k3 ^= (FT_UInt32)tail[9] << 8;
+        /* fall through */
       case 9:
         k3 ^= (FT_UInt32)tail[8];
         k3 *= c3;
         k3  = ROTL32( k3, 17 );
         k3 *= c4;
         h3 ^= k3;
+        /* fall through */
 
       case 8:
         k2 ^= (FT_UInt32)tail[7] << 24;
+        /* fall through */
       case 7:
         k2 ^= (FT_UInt32)tail[6] << 16;
+        /* fall through */
       case 6:
         k2 ^= (FT_UInt32)tail[5] << 8;
+        /* fall through */
       case 5:
         k2 ^= (FT_UInt32)tail[4];
         k2 *= c2;
         k2  = ROTL32( k2, 16 );
         k2 *= c3;
         h2 ^= k2;
+        /* fall through */
 
       case 4:
         k1 ^= (FT_UInt32)tail[3] << 24;
+        /* fall through */
       case 3:
         k1 ^= (FT_UInt32)tail[2] << 16;
+        /* fall through */
       case 2:
         k1 ^= (FT_UInt32)tail[1] << 8;
+        /* fall through */
       case 1:
         k1 ^= (FT_UInt32)tail[0];
         k1 *= c1;

src/smooth/ftgrays.c

@@ -1244,14 +1244,29 @@ typedef ptrdiff_t  FT_PtrDist;
        */
       switch ( acount )
       {
-      case 7: *q++ = c;
-      case 6: *q++ = c;
-      case 5: *q++ = c;
-      case 4: *q++ = c;
-      case 3: *q++ = c;
-      case 2: *q++ = c;
-      case 1: *q   = c;
-      case 0: break;
+      case 7:
+        *q++ = c;
+        /* fall through */
+      case 6:
+        *q++ = c;
+        /* fall through */
+      case 5:
+        *q++ = c;
+        /* fall through */
+      case 4:
+        *q++ = c;
+        /* fall through */
+      case 3:
+        *q++ = c;
+        /* fall through */
+      case 2:
+        *q++ = c;
+        /* fall through */
+      case 1:
+        *q = c;
+        /* fall through */
+      case 0:
+        break;
       default:
         FT_MEM_SET( q, c, acount );
       }