updated libmikmod changelog.
configure.ac: link mingw builds with -static-libgcc
drv_wasapi: improve playback stability under heavy system load, support MMCSS "Pro Audio"
Cherry-picked the commit to master. Applied a few follow-up commits: Make sure all are OK.
win32/Makefile.mingw: link with -static-libgcc.
README: update documentation for wasapi default audio buffer size.
wasapi: add comment about actual param type of AvSetMmThreadPriority()
wasapi: use ANSI apis with avrt.dll instead of USICODE.