If reading the header fails, the demuxer's read_close() function (if
existing) is not called automatically; instead several demuxers call it
via "goto fail" in read_header().
This commit intends to change this by adding an internal flag for
demuxers that can be used to set on a per-AVInputFormat basis whether
read_close() should be called generically after an error during
read_header().
The flag controlling this behaviour needs to be added because it might
be unsafe to call read_close() generally (e.g. this might lead to
read_close() being called twice and this might e.g. lead to double-frees
if av_free() is used instead of av_freep(); or a size field has not
been reset after freeing the elements (see the mov demuxer for an
example of this)).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>