Add code comment for expr_emit_tagged
Explicitly manage free register operand in jump and test instructions
Improve bytecode generation for ISTC/ISFC instructions
Extend system to keep trace of loops in bytecode generation

Useful to correctly set the jump free register operand in "break"
instructions.
Improve JUMP instruction generation for break statement
Implement LuaJIT bytecode gen compatibility fix
Fix the register number generation in while loop