fb: Silence warnings when building with clang

fbpict.c:163:8: warning: implicit conversion from enumeration type 'PictFormatShort' (aka 'enum _PictFormatShort') to different enumeration
      type 'pixman_format_code_t' [-Wconversion]
        pict->format,
        ~~~~~~^~~~~~

fbbltone.c:486:2: warning: shift result (281474959933440) requires 49 bits to represent, but 'int' only has 32 bits [-Wshift-overflow]
        C2_24( 0, 0), C2_24 ( 1, 0), C2_24 ( 2, 0), C2_24 ( 3, 0),
        ^~~~~~~~~~~~
fbbltone.c:474:6: note: instantiated from:
     SelMask24(b,1,r))
     ^
fbbltone.c:429:46: note: instantiated from:
                                                    ^
fbbltone.c:427:18: note: instantiated from:
                      0xffffff << Mask24Check(x,r)) : 0)
                      ~~~~~~~~ ^

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>
Reviewed-by: Jamey Sharp <jamey@minilop.net>

fb/fbbltone.c

@@ -26,6 +26,11 @@
 
 #include "fb.h"
 
+#ifdef __clang__
+/* shift overflow is intentional */
+#pragma clang diagnostic ignored "-Wshift-overflow"
+#endif
+
 /*
  *  Example: srcX = 13 dstX = 8	(FB unit 32 dstBpp 8)
  *

fb/fbpict.c

@@ -160,7 +160,7 @@ create_bits_picture (PicturePtr pict,
     fbGetPixmapBitsData(pixmap, bits, stride, bpp);
 
     image = pixman_image_create_bits (
-	pict->format,
+	(pixman_format_code_t)pict->format,
 	pixmap->drawable.width, pixmap->drawable.height,
 	(uint32_t *)bits, stride * sizeof (FbStride));