* Remove dependency on SDL.h where possible
 * Use run-time linking where possible
 * Support both SDL 1.2 and SDL 2
 * Add device enumeration when using SDL 2

The Emscripten build currently uses SDL 1.2 because it avoids the need
for "-s USE_SDL=2" when compiling. This may change later if there's
ever a need or if there's enough demand.

extend with PD MOD/XM player

Not quite sure what I was originally thinking with these. Much better
now.

Add macOS library names

This API is a helper for doing a bulk format conversion in one go.