[Ohrrpgce] SVN: teeemcee/8458 Fix crash on Unix if libSDL_mixer.so not found; not searching for a .dll

[subversion at HamsterRepublic.com]

teeemcee
2017-02-27 15:55:58 -0800 (Mon, 27 Feb 2017)
224
Fix crash on Unix if libSDL_mixer.so not found; not searching for a .dll on Windows; and not working on Android

Turns out that on Unix it's not valid to pass NULL to dlclose,
and both glibc and bionic crash, but not Windows
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U   wip/music_sdl.bas