Improve branch code generation
Remove -mmemory-latency flag

It doesn't do the right thing and it's a uarch-specific setting that belongs
in the machine description.
Handle more FP unordered comparisons
Emit NOT pseudo-op instead of XORI -1

This is only for assembly readability.
Improve int32 performance on RV64
Minor glibc cleanups
gcc cleanup
more gcc cleanup
gcc cleanup
Handle far branches in GAS, not GCC

Because of relaxations, GAS has better information about branch distances, and
so this improves code generation.  And it's simpler.
gcc cleanup
gcc cleanup
gcc cleanup
Remove Hwacha code generation support

The plan is to use LLVM to generate code for this nonstandard ISA extension.
gcc cleanup
Stub out riscv_fallback_frame_state

This needs to be implemented eventually.