Add breakpoints to x86 jit for easier debugging.

They should be really fast so leaving them on in release.
Clear jit cache when changing breakpoints.

For now, only when paused.  I don't think clearing the cache while
running is an awesome idea.
Correctly break at branch points in x86 jit.
Add breakpoints for delay slots.

Wanted to do this in CompileAt(), darn not nice delay slots.
Refactor out all the CheckJitBreakpoint()s.

Ah, much cleaner.
Merge pull request #439 from unknownbrackets/jit-minor2

Jit breakpoints (x86 only)