add SDL_mixer

libs/SDL_mixer/external/opusfile/.gitignore

@@ -0,0 +1,49 @@
+*.a
+*.exe
+*.la
+*.lo
+*.o
+*.sw*
+*~
+.deps
+.dirstamp
+.libs
+/Makefile
+Makefile.in
+aclocal.m4
+autom4te.cache/
+config.guess
+config.log
+config.status
+config.sub
+configure
+config.h.in
+config.h
+compile
+depcomp
+doc/Doxyfile
+doc/doxygen-build.stamp
+doc/html
+doc/latex
+examples/opusfile_example
+examples/seeking_example
+install-sh
+libopusfile-*.tar.*
+libtool
+ltmain.sh
+m4/libtool.m4
+m4/ltoptions.m4
+m4/ltsugar.m4
+m4/ltversion.m4
+m4/lt~obsolete.m4
+missing
+opusfile.pc
+opusfile-uninstalled.pc
+opusurl.pc
+opusurl-uninstalled.pc
+package_version
+stamp-h1
+test-driver
+unix/objs
+unix/opusfile_example
+unix/seeking_example