Commit a2d28010cc ("cleanup: find_subfiles.c: simplify (mainly using
bstr)") was missing a bstrdup() in subtitle search code, and thus the
code erroneously modified the original filename string passed in. As a
result anything which printed or otherwise used the filename after
that would use a lowercase-converted version instead of the actual
file name. Fix by adding the bstrdup() to operate on a local copy of
the name instead.
A file with the ambiguous extension .sub could be either VOBsub or
MicroDVD. If there's a corresponding .idx file it's certainly VOBsub,
so don't add it to the list of potential text subtitles. This will
avoid the annoying warning "SUB: Could not determine file format".
Analogously to the previous commit, move path handling logic for
loading external vobsub files from mplayer.c to find_subfiles.c.
Based on a commit from Clément Bœsch but fixed and simplified.
Move path handling for loading external subtitle files from mplayer.c
to find_subfiles.c. Now the remaining code in mplayer.c only gets a
list of potential filenames and tries opening those.
Move sub_filenames() and related code from subreader.c to new file
find_subfiles.c. This function is used to find subtitle files that
should be loaded for the current video; this functionality is not
specific to the particular kind of text subtitle handling implemented
in subreader.c.
Also reindent and prettify the moved code a bit.
