added missing externs (we were lucky that commons are used)

Originally committed as revision 659 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.h

@@ -434,8 +434,8 @@ void MPV_frame_end(MpegEncContext *s);
 #ifdef HAVE_MMX
 void MPV_common_init_mmx(MpegEncContext *s);
 #endif
-int (*dct_quantize)(MpegEncContext *s, DCTELEM *block, int n, int qscale, int *overflow);
-void (*draw_edges)(UINT8 *buf, int wrap, int width, int height, int w);
+extern int (*dct_quantize)(MpegEncContext *s, DCTELEM *block, int n, int qscale, int *overflow);
+extern void (*draw_edges)(UINT8 *buf, int wrap, int width, int height, int w);
 void ff_conceal_past_errors(MpegEncContext *s, int conceal_all);
 void ff_copy_bits(PutBitContext *pb, UINT8 *src, int length);
 void ff_clean_intra_table_entries(MpegEncContext *s);