[LinuxCNC/linuxcnc Issue#505] multi-spindle: python interface `cmd.brake` missing optional spindle argument.

1. run sim/axis/lathe_multispindle/lathe.ini
2. reset and turn machine on
3. start a interactive python session and run:
“python
>>> import linuxcnc
>>> s = linuxcnc.stat()
>>> c = linuxcnc.command()
>>> s.poll(); s.spindle[0]['brake']
1L
>>> c.brake(0) # release spindle 0 brake
>>> s.poll(); s.spindle[0]['brake']
0L
>>> s.poll(); s.spindle[1]['brake']
1L
>>> c.brake(0, 1) # release spindle 1 brake
Traceback (most recent call last):
File "", line 1, in
TypeError: function takes exactly 1 argument (2 given)
>>>
“