sal logging: Flush after having written the output.

Makes it possible to see the messages immediately on Windows; otherwise the
SAL_DEBUG() etc. is useless as it shows on screen too late.

Change-Id: I701922aa4fcacf66d6b044e0badca7ef1f9cac94
OpenGLContext: Use the right window handle on Windows.

Change-Id: I77eaf1dad9ce4c855b5f88bd8568944fd4128227
Use WB_CLIPCHILDREN consistently.

Change-Id: Ifd53e37d23c29efb2f084a39b48c88ea4bc0d70a