[truetype] Fix integer overflow.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35312

* src/truetype/ttinterp.c (Ins_JMPR): Use `ADD_LONG`.

ChangeLog

@@ -1,3 +1,13 @@
+2021-06-19  Werner Lemberg  <david@freetype.org>
+
+	[truetype] Fix integer overflow.
+
+	Reported as
+
+	  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35312
+
+	* src/truetype/ttinterp.c (Ins_JMPR): Use `ADD_LONG`.
+
 2021-06-19  Werner Lemberg  <david@freetype.org>
 
 	[autofit] Prevent hinting if there are too many segments.

src/truetype/ttinterp.c

@@ -3593,7 +3593,7 @@
       return;
     }
 
-    exc->IP += args[0];
+    exc->IP = ADD_LONG( exc->IP, args[0] );
     if ( exc->IP < 0                                             ||
          ( exc->callTop > 0                                    &&
            exc->IP > exc->callStack[exc->callTop - 1].Def->end ) )