EMC stepper & misc fixes

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