Fix crash on Return to Menu in Symbian.
We don't want to free the executable code (actually a Chunk+Heap) using same method we use to free memory pages (delete).
This would be the same situation on jailbroken iOS and WP.
Now the JIT code is always allocated and never freed on Symbian.
Merge pull request #754 from unknownbrackets/quit-fix

Fix crash on quit / pause not working
Add more imm handling for shifts in x86 jit.

This is actually hit, and propagates more imms through.
Optimize addi/addiu to just LEA when possible.
Optimize out some addu/etc. calls against imms.
Optimize out slti in the x86 jit.

I'm kinda surprised this actually happens...
Implement ins and ext in the x86 jit.
Add a stub for clz/clo in x86 jit.