Reverted previous changes and added a hopeful solution for lack of window realization
A few changes concerning wxGTK.

For one, I added a new member gs_window for future use.
The member is "display" which represents our connection to X11.
Ideally, we should use this specific connection to deal with our Window.
For now, it's disabled. Read comment for more information.

Secondly, wxGTK apparently doesn't map our window in some cases.
This causes the window ID passed to be bad and will stop (or segfault)
our program. This might be related to the first commit above.

For now, all this commit does is realize the window manually.
Cleaned up a bit, reverted API back to normal
Added comments on why some code is disabled
Fixed os_gettime_ns to provide correct time in ns
Merge pull request #25 from computerquip/upstream-merged

Various changes for wxGTK
Add copyright and name to files it applies to.
Merge with upstream-merged