Fix Windows Method

[mhils]

The Windows method was a bit unstable on my system, so I decided to rewrite it in the most cautious way possible based on the MSDN docs

• GlobalAlloc is called with GMEM_MOVEABLE as required by SetClipboardData
• We do the full dance and pass a valid hwnd to OpenClipboard, as required by the SetClipboardData docs
• If OpenClipboard fails the first time, we repeatedly try to get the clipboard lock for up to 500ms.
• Fixed support for Python 3.5 x64 (HANDLE apparently as different sizes on x32 and x64, thus we must specify argtypes and restype for each API call)
• Every Windows API call gets now checked for potential errors
• Removed .decode('mbcs') call. On Python 2.7, c_wchar_p apparently auto-converts bytes to unicode. On Python 3.5, calling the method with bytes returns a fairly descriptive TypeError: unicode string or integer address expected instead of bytes instanceerror. If there are issues with that, there should be tests to cover this.
• Given the verbosity, I moved the Windows-specific code in its own file.

This should fix #5, fix #7, fix #10, fix #16, fix #21, fix #25.
It should also fix #27 and #35 by making them obsolete.

[asweigart]

Thanks a lot for this patch! The problem that's been happening between 32 and 64-bit was one I haven't been able to get to, but this should fix a lot of people's Pyperclip problems.