Refactor the renderer and sound media systems into a shared / reusable lib

[Jay Dolan]

The goals of the refactor should be:

1. Commonize r_media_t and s_media_t into a single struct.
2. Simplify dependency management, perhaps by using an "aggregate root" approach and stateful loading function.
3. Support media aliasing directly so that sexed model sounds do not require any additional work.

This work does not, and should not, block the 1.0 release. This is lower priority.

[Jay Dolan]

This is honestly pointless. It'd be a fair amount of work to save 100 lines of code.