install dsputil.h, that is used by many filters in mplayer

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@4825 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/Makefile

@@ -515,6 +515,8 @@ install-headers:
 	mkdir -p "$(prefix)/include/ffmpeg"
 	install -m 644 $(SRC_PATH)/libavcodec/avcodec.h \
                 "$(prefix)/include/ffmpeg"
+	install -m 644 $(SRC_PATH)/libavcodec/dsputil.h \
+                "$(prefix)/include/ffmpeg"
 	install -d "$(libdir)/pkgconfig"
 	install -m 644 ../libavcodec.pc "$(libdir)/pkgconfig"