Add generic HIOP instruction for extra backend functionality.
Add support for HIOP to x86 backend.
Use POWI for 64 bit integer x^k, too.
POWI is lowered to a call by SPLIT or the x64 backend.
IR_KPTR holds a const pointer to possibly non-const content.
IR_KKPTR holds a const pointer to definitely const content.
Note that only content known by the VM to be const qualifies.
Content tagged as const by users (e.g. const char *) doesn't.
Compile math.sinh(), math.cosh(), math.tanh() and math.random().
Compile various io.*() functions.
Drive the GC forward on string allocations in the parser.
Improve KNUM fuse vs. load heuristics.
Add abstract C call handling to IR.
