AWT clipping performance on Windows can be significantly improved

The ReleaseDC() method in AwtGraphics contains a redundant call to LogicalSelectClipRgn.

This comment is extracted from an email message received from the actual submitter of this bug report, Armin Ebrahimi <###@###.###>:
"It is not necessary to reset the clip region to NULL since each thread calls either GetDC or ValidateDC which in turn sets the clipping region. Removing
this call provides for a substantial improvement when clipping is enabled."

Armin has measured a performance improvement of up to 50% for clipped AWT calls (e.g., draw line, rectangle, and oval drawing, etc).