* Prototype gcode infix math, very basic.
* Adding exprtk math parser library, header only.
@ArashPartow
https://github.com/ArashPartow/exprtk@4e1315a87dcc99a1ccad21fae1def0c2d4913c0f
* Now evaluating strings with exprtk, only support no variables in input
strings.
* Moved executable code to cpp file, stubbed out xsp and let the testing begin...
* Added conditional gcode parser into export path, added tests.
* Added one more test to ensure that {if0} only removes up to newlines.
* Test failure to parse
* Add some compiler flags to compile out stuff from exprtk
* Fix debug messages to be more specific, don't use deleted stringstream = method.
* Trade expression speed for apparently around 50MB of object size.
* Removed an extra trim that was breaking existing tests.
* fix test
Fixes#3390
