IR element for loop control flow breaks
AST -> IR back references
Seems to be sound in external tests

The bytecode is messy, though. The nasty ASM
nop / athrow frames strike back!
Test for break / continue
Avoid the NOP/ATHROW invalid frames

This typically happens with else branches code, as the GOTO yields dead code for ASM while computing
frames.

A cleaner approach is to be investigated, but meanwhile the JIT should easily understand that the
jump condition is 100% stable given that the comparison happens to be on a constant...
Test to check for incorrect break/continue
Document break and continue
Merge pull request #4 from jponge/wip-break-statement

Break and continue statements