Prevent unknown getpointer in sceKernelMemset

Fix #7064
Add some jit benchmarking code.
Cut down on test overhead a good bit.
x86jit: Implement other forms of vx2i.

Gains 3.2% performance in Grand Knights History.
Merge pull request #7065 from sum2012/memset

Prevent unknown getpointer in sceKernelMemset
Merge pull request #7067 from unknownbrackets/jit-bench

Add some jit benchmarking code
Merge pull request #7068 from unknownbrackets/jit-minor

x86jit: Implement other forms of vx2i