oslibs (macosx, windows):  recompile libFLAC with malformed
vorbiscomment handling improvements from git and with a fix
for windows vsnprintf().


git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk@1068 af15c1b1-3010-417e-b628-4374ebc0bcbd