[patch #3268] Run Loops with WaitForMultipleObjects in Mingw

[Luis Cabellos]

Past weeks I had working in a Fix for [bug #7952] and now it is. For 
mingw32 I have change the select(...) call in -[pollUntil: milliseconds 
within: contexts] method with a call to win32 function 
MsgWaitForMultipleObjects(...). Also in classes that use AddEvent, 
instead of use a file descriptor now use a win32 Handle.

I had refactoring the NSRunLoop.m file to put out some classes and had 
different version (the old, and de new of win32).

All this changes affect only the mingw32 version of GNUstep, everything 
else remains equal.

With the patch also I had attached a README file with a detailed explain 
of the changes.

And that's is all.

Luis Cabellos | Tragnarion Studios