Fix a bunch of casts in the x86 recompiler core.

There are a load of casts from pointers to 'int' and 'u32' in the JIT core.
This takes a better practices approach to the problem and casts to uptr instead.
Zero functionality change of course, just changes all of these terrible casts to going to uptr which makes the casting style consistant and work on
both x86_32 and x86_64.

This obviously doesn't work around the issue of the recompiler not running on x86_64, but we need compiling before we delve further.