glwindow: Close Windows GDI handles for fonts on exit

I think the handles are automatically deleted by OS on process
termination, but I have been experiencing strange effect that
the OS's fonts become weird, so it may help.

For the issue's details, see commit 2f7a7cf.

I also tried FreeType library and its OpenGL adapter, freetype-gl,
in order to replace Windows GDI, but it turned out that the libraries
need so much effort to optimize to catch up Windows GDI's performance.
Optimize location window by omit drawing unvisible items

The warp destination window (and teleport window) can be so slow
when the listed items are so many.  We can omit drawing items
whose position is out of frame.
Further improve location window's performance

Reduces count of filter methods calls to minimum required.
Tweak galaxy's blob sprite in the hope it looks smoother

Previous image had gradually darkening border which make each blob
sprite look separated.  The image's RGB channels are altered with
flat perlin noise to make a bunch of sprites looks one piece.