100l: Remove stray character that slipped into header name.

Originally committed as revision 17231 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1013,7 +1013,7 @@ mpeg2video_encoder_select="aandct"
 mpeg4_encoder_select="aandct"
 mpeg_vdpau_decoder_deps="vdpau"
 mpeg1_vdpau_decoder_deps="vdpau"
-mpeg_xvmc_decoder_deps="X11_extensions_XvMClibx_h"
+mpeg_xvmc_decoder_deps="X11_extensions_XvMClib_h"
 msmpeg4v1_encoder_select="aandct"
 msmpeg4v2_encoder_select="aandct"
 msmpeg4v3_encoder_select="aandct"