There's a single mp_msg() in path.c, but all path lookup functions seem
to depend on it, so we get a rat-tail of stuff we have to change. This
is probably a good thing though, because we can have the path lookup
functions also access options, so we could allow overriding the default
config path, or ignore the MPV_HOME environment variable, and such
things.
Also take the chance to consistently add talloc_ctx parameters to the
path lookup functions.
Also, this change causes a big mess on configfiles.c. It's the same
issue: everything suddenly needs a (different) context argument. Make it
less wild by providing a mp_load_auto_profiles() function, which
isolates most of it to configfiles.c.
Remove the ifdef hell from mp_find_user_config_file(). Move the win32
specific code (for MinGW and Cygwin) to path-win.c. The behavior should
be about the same, but I can't be sure due to lack of testing and
because the old path.c code was hard to follow. (I expect those who care
about windows will fix things, should issues pop up - sorry.)
One difference is that the new code will always force MPV_HOME. It looks
like the old code preferred the mpv config dir in the exe dir if it
exists.
Also, make sure MP_PATH_MAX has enough space, even if the equivalent
wchar_t string is not 0-terminated with PATH_MAX (because apparently the
winapi doesn't require this). (Actually, maybe we should just kill all
uses of PATH_MAX/MP_PATH_MAX.)