Let GButton have an optional icon (GraphicsBitmap) that gets rendered in the
middle of the button if present.
Also add GraphicsBitmap::load_from_file() which allows mmap'ed RGBA32 files.
I wrote a little program to take "raw" files from GIMP and swizzle them into
the correct byte order.
Use this to fix a use-after-free in ~GraphicsBitmap(). We'd hit this when
the WindowServer was doing a deferred destruction of a WSWindow whose
backing store referred to a now-reaped Process.
Instead of clients painting whenever they feel like it, we now ask that they
paint in response to a paint message.
After finishing painting, clients notify the WindowServer about the rect(s)
they painted into and then flush eventually happens, etc.
This stuff leaves us with a lot of badly named things. Need to fix that.
Make PageDirectory retainable and have each Region co-own the PageDirectory
they're mapped into. When unmapped, Region has no associated PageDirectory.
This allows Region to automatically unmap itself when destroyed.
