sws: avoid signed C99 overflows

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libswscale/swscale.c

@@ -848,33 +848,33 @@ int attribute_align_arg sws_scale(struct SwsContext *c,
             y = av_clip_uint8((RY * r + GY * g + BY * b + ( 33 << (RGB2YUV_SHIFT - 1))) >> RGB2YUV_SHIFT);
             u = av_clip_uint8((RU * r + GU * g + BU * b + (257 << (RGB2YUV_SHIFT - 1))) >> RGB2YUV_SHIFT);
             v = av_clip_uint8((RV * r + GV * g + BV * b + (257 << (RGB2YUV_SHIFT - 1))) >> RGB2YUV_SHIFT);
-            c->pal_yuv[i]= y + (u<<8) + (v<<16) + (a<<24);
+            c->pal_yuv[i]= y + (u<<8) + (v<<16) + (a<<24U);
 
             switch (c->dstFormat) {
             case AV_PIX_FMT_BGR32:
 #if !HAVE_BIGENDIAN
             case AV_PIX_FMT_RGB24:
 #endif
-                c->pal_rgb[i]=  r + (g<<8) + (b<<16) + (a<<24);
+                c->pal_rgb[i]=  r + (g<<8) + (b<<16) + (a<<24U);
                 break;
             case AV_PIX_FMT_BGR32_1:
 #if HAVE_BIGENDIAN
             case AV_PIX_FMT_BGR24:
 #endif
-                c->pal_rgb[i]= a + (r<<8) + (g<<16) + (b<<24);
+                c->pal_rgb[i]= a + (r<<8) + (g<<16) + (b<<24U);
                 break;
             case AV_PIX_FMT_RGB32_1:
 #if HAVE_BIGENDIAN
             case AV_PIX_FMT_RGB24:
 #endif
-                c->pal_rgb[i]= a + (b<<8) + (g<<16) + (r<<24);
+                c->pal_rgb[i]= a + (b<<8) + (g<<16) + (r<<24U);
                 break;
             case AV_PIX_FMT_RGB32:
 #if !HAVE_BIGENDIAN
             case AV_PIX_FMT_BGR24:
 #endif
             default:
-                c->pal_rgb[i]=  b + (g<<8) + (r<<16) + (a<<24);
+                c->pal_rgb[i]=  b + (g<<8) + (r<<16) + (a<<24U);
             }
         }
     }