EMC fixes

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

EMC folks,

There's a new release on the FTP site, dated 16 June. It contains fixes to the
part program verify feature, to a problem that prevented some errors from
popping up on the display.

To verify a part program, first open it, then click the "Verify" button in the
same row as the program-related buttons, or type "v". The program is run
and checked for syntax, picky cutter comp gouging, machine limits, etc.

I also fixed some stepper motor timing that caused problems if you set the
[TRAJ] MAX_VELOCITY and [AXIS_*] INPUT_SCALE to values that made the stepper
pulse task run so fast that it starved the communication link.

--Fred