Initial take on subsystems support.
Small bugfix and docs fix.
Fix autosave toggle bug.
Cleanup block sram overwrite.
More verbose logging of subsystems.
Rename to SET_SUBSYSTEM_INFO.

Add test case.
Add support for ZIP extraction to temporary folders.
Correctly pass NULL when we load no ROM.
Merge pull request #636 from libretro/subsystem

libretro subsystem API