constant: Use dir(comedi.wrapped) when comedi.wrapped exists

Since 371dcc5 (swig: remove comedi_ prefix from the function names,
2014-01-31, released in comedilib 0.10.2), dir(comedi) no longer lists
the meaty-bits:

  >>> import comedi
  >>> comedi.CR_ALT_FILTER
  67108864
  >>> [attr for attr in dir(comedi) if attr.startswith('CR_')]

Instead, they have shifted to comedi.wrapped:

  >>> [attr for attr in dir(comedi.wrapped) if attr.startswith('CR_')]
  ['CR_ALT_FILTER', 'CR_ALT_SOURCE', 'CR_DEGLITCH', 'CR_DITHER', 'CR_EDGE',
   'CR_FLAGS_MASK', 'CR_INVERT']

This commit adjusts pycomedi to use comedi.wrapped when it exists, so
pycomedi will work with the new comedilib (and continue working with
the old comedilibs).

I also have to remove 'COMEDI_' from the prefixes that contain it to
catch up with 371dcc5:

  +%rename("%(strip:[COMEDI_])s", regextarget=1) "COMEDI_.*";

Reported-by: Colin Jermain <clj72@cornell.edu>
constant: Avoid non-integer values in _Enum

When my lowercase names collide (e.g. for COMEDI_TO_PHYSICAL and
comedi_to_physical), we want to add the integer value to the enum, not
the function value.  This avoids:

  >>> from pycomedi.device import Device
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "instruction.pxd", line 22, in init pycomedi.device (pycomedi/device.c:4532)
    File "instruction.pyx", line 25, in init pycomedi.instruction (pycomedi/instruction.c:2427)
    File "chanspec.pyx", line 20, in init pycomedi.chanspec (pycomedi/chanspec.c:2571)
    File "constant.pyx", line 469, in init pycomedi.constant (pycomedi/constant.c:10017)
    File "constant.pyx", line 244, in pycomedi.constant._Enum.__init__ (pycomedi/constant.c:3804)
    File "constant.pyx", line 260, in pycomedi.constant._Enum._add_item (pycomedi/constant.c:4305)
  TypeError: unorderable types: builtin_function_or_method() < int()

I'm not sure how I haven't bumped into this before.  Perhaps Cython
0.19.1 has stronger type-checking for its comparison operaters than my
old 0.17.4.