added CompileEnv and lens for it
Added gwhile to generate Fanuc macro while, they're needed in tight processing loops, where gotos stopping machine for a split of second are undesirable
added support for breaks inside gWhile
in case 'if' contains only a goto skip generating a separate code block for it, just put it into the 'gIf' body
Merge branch 'codegen' of github.com:akamaus/gcodec into experiments