gcode development

1. Implement plane switching to support milling (in progress)


2. 3D view (OpenGL, also in progress)


3. Move path discretization code into the kernel, support in-program fast feeds, pauses. I deferred this till "later times", and now this seems to be the right decision: the implementation I had in mind before looks flawed to me now.


4. Support EMC's rs274ngc interpreter (some initial adoption has been done already). This interpreter is a nice option, but in its current form it is not suitable for 4-axis wire EDM, so the current interpreter is not going away.

Hope to finish this before it gets warm and dry. Then, if all goes well, another real-world testing session will follow, during which probing support is to be added.

Future plans and thoughts include more compatibility with EMC: become compatible with HAL, and make -mync real-time kernels an option for RTAPI. I've investigated into it recently, and it looks perfectly possible.