== DETAILS
I think this will fix the problem with duplicate pads--pads weren't properly
de-initializing and registering as disconnected. When a pad is disconnected,
the slot should properly release now.
retro_bits_t turned into input_bits_t and there were parts of my
code that needed to update.
== TESTING
No idea if upstream changes broke anything, but it compiles cleanly
now.
Fortunately, the gcc port implements the builtins and, from basic
testing, they seem to work.
This is only really useful on Wii U--other platforms have more
robust atomic operations, or aren't using gcc to build.
