Fix a bug in the ARMEmitter.

When creating a Fixupbranch we were swapping the BL and B targets.
I think this was found by PPSSPP a while ago, but they never send PRs to merge their changes upstream.
Fix Fastmem on ARM once more.
Fix trailing whitespace.
Remove dumb CodeBlock duplication in the emitters.
Fixes issue 6990.
This uses a bit of templating to remove the duplicate code that is the CodeBlocks in each emitter headers.
No actual functionality change in this.
[ARM] Minor cleanup to lXX and stX. Fixes a bug.
Fixes an issue in lXX where if the instruction was an update instruction and was a register address offset that we would add garbage values to the
writeback register.
Does some minor cleanups as well which save a few instructions here and there.
[ARM] Implements more fastmem instructions in lXX.
There are a few instructions in lXX that aren't currently fastmem capable due to using a register offset.
This implements fastmem for those few instructions.
Really I'll be changing how ARMv7 fastmem works in the future so this is really temporary code.
Just don't know how long it'll stay.
This relies on PR #257