[LinuxCNC/linuxcnc PR#147] M30 remap interaction lcnc26

From emc-developers:

> I found a buglet where an M30 or M02 in the same block as a remapped
> command triggers the error ‘BUG: remap_level < 0 : -1'. This bug must > have previously escaped attention because this is a rarely-encountered
> corner case.
>
> I discovered it while cutting parts on a PCNC 1100, where M06 is
> remapped, with a program generated by the HeeksCNC ’emc2b’ post
> processor, which terminates programs with ‘T0 M06 M02’.
> —
>
> A buildbot job with just the unit test demonstrates the bug:
>
> http://buildbot.linuxcnc.org/buildbot/builders/0000.checkin/builds/4447
>
> Search for the string ‘remap/m30-interaction’ in a failed ‘runtests’
> build step, as here:
>
>

> http://buildbot.linuxcnc.org/buildbot/builders/1400.rip-wheezy-i386/builds/2591/steps/runtests/logs/stdio
> 

>
> The one-liner fix is applied against the 2.6 branch:
>
> http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=shortlog;h=refs/heads/zultron/m30-remap-interaction-lcnc26
>
> Another buildbot job is currently running to test the fix:
>
> http://buildbot.linuxcnc.org/buildbot/builders/0000.checkin/builds/4448