DrawCaption() now works, and is called (unsurprisingly) for drawing the captions...

DrawCaption() now works, and is called (unsurprisingly) for drawing the captions of windows!

* Implemented DrawCaption() in lib/user32/windows/defwnd.c (couldn't put it in draw.c due to the functions it relies upon being in defwnd.c)
* Changed a few metrics in subsys/win32k/ntuser/metric.c to match the Windows defaults
* Added DC_GRADIENT and DC_BUTTONS to include/defines.h
* Modified prototype for UserDrawSysMenuButton in lib/user32/include/window.h to return success/failure
* Modified lib/usr32/resources/obm_close.bmp slightly. It now looks more like the Windows version.

svn path=/trunk/; revision=5688