EMC stepper & misc fixes

[proctor-at-cme.nist.gov (Fred Proctor)]

EMC users,

I just put a new release of the EMC code on the FTP site. This contains a fix
to the following error abort action and some new features. Thanks to Tim
Goldstein for pointing these out. Details:

1. The following error abort code only looked at errors in one direction. This
explains why the following errors only kicked in half the time. I wonder how
this went uncorrected so long. Perhaps we were blaming hardware?    

2. Part program verification. Forget about the "rs274ngc" command-line utility 
I mentioned. There is now a "Verify" button on the xemc GUI. Click this after
you've opened a part program and it will run through checking syntax, cutter
comp gouging, limit violations, etc. Let me know how well this works.

3. Stepper motor setup is less painful, hopefully. In your .ini file, set the
steps-per-unit value in the [AXIS_*] INPUT_SCALE line for each motor, and the
maximum feed rate you want in the [TRAJ] MAX_VELOCITY line. The cycle time for
the stepper task is calculated automatically. Note that you still have to
tune the MAX_VELOCITY so that you don't exceed your motor capabilities or
run the stepper task so fast you starve everything else.

See the emc/doc/RELEASE_NOTES, aka emc-14-Jun-1999.txt on the FTP site, for
slightly more detail.   

Field experiences greatly appreciated. Happy Flag Day.

--Fred