This cleans up a few problems with our use of the ancient ALSA 0.9 API.

This means we can ditch the dlvsym() nonsense and use SDL_LoadFunction(), too.

 Fixes Bugzilla #745.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%404006