[MingW] Multithreading applications do not work

[Wim Oudshoorn]

If no one objects I will commit this patch.

Problem
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On MinGW if a program becomes multithreaded it will bail out.


Reason
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If a program becomes multithreaded GSPerformHolder will be set up.
This in turn will create a pipe to communicate between threads.
However pipes are not sockets and when it registers the 
pipe (non-socket) with the runloop of the default thread 
it will bail out because the runloop does not understand
pipes


Solution
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Temporary solution is to remove the offending code on MinGW.
This will break performSelectorOnMainThread methods, but at
least multithreading will work.

(This is a short term solution)


Wim Oudshoorn.