add optional dependency on gtop. Include "(as username)" in the titlebar

	* configure.in: add optional dependency on gtop.
	* src/core/window-props.c: Include "(as username)"
          in the titlebar if a window is running as another user.
	* src/core/window.c: check for PID before name, since
          the rendering of the name can now depend on the PID.
        Closes #549389.


svn path=/trunk/; revision=4181