Use meld in Cygwin

[Jie Zhang <jzhang918 gmail com>]

Hi,

It has been for a while that meld can not be used in cygwin. I tried
to bisect the commit which caused it. Below is what I found.

1. commit 8463b8 caused a crash when starting meld in cygwin:

$ ./bin/meld

** (process:4740): WARNING **: Trying to register gtype
'GMountMountFlags' as enum when in fact it is of type 'GFlags'

** (process:4740): WARNING **: Trying to register gtype
'GDriveStartFlags' as enum when in fact it is of type 'GFlags'

** (process:4740): WARNING **: Trying to register gtype
'GSocketMsgFlags' as enum when in fact it is of type 'GFlags'
/usr/lib/python2.7/site-packages/gobject/__init__.py:115: Warning:
attempting to add an interface (GtkEditable) to class
(HistoryFileEntry) after class_init
  type_register(cls, namespace.get('__gtype_name__'))
Traceback (most recent call last):
  File "./bin/meld", line 164, in <module>
    main()
  File "./bin/meld", line 146, in main
    import meld.meldapp
  File "/cygdrive/c/meld/meld/meldapp.py", line 171, in <module>
    from . import filediff
  File "/cygdrive/c/meld/meld/filediff.py", line 62, in <module>
    process_pool = multiprocessing.Pool(None, init_worker, maxtasksperchild=1)
  File "/usr/lib/python2.7/multiprocessing/__init__.py", line 232, in Pool
    return Pool(processes, initializer, initargs, maxtasksperchild)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 115, in __init__
    self._setup_queues()
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 210, in _setup_queues
    self._inqueue = SimpleQueue()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 352, in __init__
    self._rlock = Lock()
  File "/usr/lib/python2.7/multiprocessing/synchronize.py", line 147,
in __init__
    SemLock.__init__(self, SEMAPHORE, 1, 1)
  File "/usr/lib/python2.7/multiprocessing/synchronize.py", line 75, in __init__
    sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
OSError: [Errno 17] File exists

2. With commit 8463b8 reverted, commit b831bb7 is good, but commit
0fccdab is bad. No crash dump. Meld just does not start.


Thank you.
Jie