core

Fixed some odd bugs in NGC flow control, prepared for file based named O-call subroutines.

Moved message substitution code from gcode.c to ngc_expr.c.

Improved parameter handling some more, now allows indirected O-calls and line numbers with O-word.

Removed misplaced code guard

Improved expression and parameter handling, simplified gcode parser related to this. Fixed typo in OR statement decode.