Fix CID: 101 Resource leak in osd_ConfigLoader (backport from b5aea372)

(cherry picked from commit 375c32ff)

Conflicts:

	src/video_output/vout_subpictures.c

Already fixed long ago on master.

block_Realloc() is a lot more intelligent in 0.9.0 nowadays, but I would
rather not commit large changes to -bugfix...

(cherry picked from commit fb04f249)

(cherry picked from commit c8075f35)

(cherry picked from commit af5aece7)

specific ... and untested :P)

We need to stick to FFmpeg r7407 for now. This mostly reverts [30b23594]. Thus, we don't need a recent GNU Make either.

Remove check for img_resample() when ffmpeg is built with libswscale. This will need to be fixed for 0.9.0 or a later bugfix release.

Refs #1594