This didn't have a header and this was implied LGPL, but this was not
entirely correct. It turns out the printf attribute code was leaked in
from talloc, which is "LGPL v3 or later". talloc was added to the
mplayer2 code base in 27a30e310e. This remaining code was an oversight.
Since we want to reduce LGPL v3 code, replace this code with the one
from ta/ta.h. This code was explicitly written newly to get rid of
talloc and its license in 0933f12d28.
This fixes the build in mingw-w64/Clang on MSYS2. It also disables the
use of gnu_printf in Clang, which was what was causing most of the
warnings. The Clang-compiled mpv binary appears to work, but there are
no guarantees yet, since until now mpv has only been tested with
mingw-w64/GCC on Windows.
Fixes#3800
bstr.c doesn't really deserve its own directory, and compat had just
a few files, most of which may as well be in osdep. There isn't really
any justification for these extra directories, so get rid of them.
The compat/libav.h was empty - just delete it. We changed our approach
to API compatibility, and will likely not need it anymore.
Just so I can move this file without modifying its contents in the next
commit.
compat/compiler.h is to be moved to osdep/ with the next commit, so add
a dummy header.
