mplayer: fix compilation with new versions of libgif

mplayer fails to compile with the following error message:

libmpdemux/demux_gif.c: In function 'demux_open_gif':
libmpdemux/demux_gif.c:260:3: error: too few arguments to function
'DGifOpen'
   gif = DGifOpen(demuxer->stream, my_read_gif);

Backport an upstream patch to support newer versions of libgif in
mplayer. Unfortunately this patch is incomplete and mplayer stills
failing to compile with a new error message:

libvo/vo_gif89a.c: In function 'uninit':
libvo/vo_gif89a.c:374:3: error: too few arguments to function
'EGifCloseFile'
   EGifCloseFile(new_gif); // also frees gif storage space.

So I have written a new patch and submitted it upstream to finally fix
the problem.

Upstream commit:

  https://github.com/pigoz/mplayer-svn/commit/a0ddaef5457e222dade386901bf448c5e3ac7b89

New submitted patch:

  https://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2015-February/072848.html

Fixes:

  http://autobuild.buildroot.net/results/a51/a510a0ab2cb827bb91b4fdec43055f2bfda239b1/



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>