Rename some forward declarations that were missed, fixes the warnings:

libavcodec/mpegvideo.o libavcodec/mpegvideo.c
libavcodec/mpegvideo.c: In function ‘MPV_frame_start’:
libavcodec/mpegvideo.c:944: warning: implicit declaration of function ‘ff_xvmc_field_start’
libavcodec/mpegvideo.c: In function ‘MPV_frame_end’:
libavcodec/mpegvideo.c:957: warning: implicit declaration of function ‘ff_xvmc_field_end’

Originally committed as revision 17258 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.c

@@ -54,8 +54,8 @@ static void dct_unquantize_h263_intra_c(MpegEncContext *s,
 static void dct_unquantize_h263_inter_c(MpegEncContext *s,
                                   DCTELEM *block, int n, int qscale);
 
-int  XVMC_field_start(MpegEncContext*s, AVCodecContext *avctx);
-void XVMC_field_end(MpegEncContext *s);
+int  ff_xvmc_field_start(MpegEncContext*s, AVCodecContext *avctx);
+void ff_xvmc_field_end(MpegEncContext *s);
 void ff_xvmc_decode_mb(MpegEncContext *s);