Rewrites ARMv7 fastmem entirely.

This is a fairly lengthy change that can't be separated out to multiple commits well due to the nature of fastmem being a bit of an intertangled mess.
This makes my life easier for maintaining fastmem on ARMv7 because I now don't have to do any terrible instruction counting and NOP padding. Really
makes my brain stop hurting when working with it.

This enables fastmem for a whole bunch of new instructions, which basically means that all instructions now have fastmem working for them. This also
rewrites the floating point loadstores again because the last implementation was pretty crap when it comes to performance, even if they were the
cleanest implementation from my point of view.

This initially started with me rewriting the fastmem routines to work just like the previous/current implementation of floating loadstores. That was
when I noticed that the performance tanked and decided to rewrite all of it.

This also happens to implement gatherpipe optimizations alongside constant address optimization.

Overall this comment brings a fairly large speedboost when using fastmem.
Merge pull request #1579 from Sonicadvance1/armv7-fastmem-rewrite

Rewrites ARMv7 fastmem entirely.