[MPlayer-dev-eng] Missing path for XviD header on Makefile

[Roberto Gordo Saez]

MPlayer cvs source fails to compile when xvid.h header is located on
some non standard place (configure --with-xvidincdir does not work).
Actually, the problem is on libavcodec Makefile, because it does not
use $(XVID_INC).

I think that libavcodec/Makefile is missing something like this:

ifeq ($(CONFIG_XVID),yes)
CFLAGS += $(XVID_INC)
endif