Revert "Try to fix behavior of volmeter popup #37"

This reverts commit 21c0b9d41345e0523c04c78b6af60a391f6f6254.

Conflicts:
	src/main.c
fix popup_window for tiling window managers
Port popup-fix to gtk3
take keyboard and pointer grab as previously expected

- you can again click the mouse pointer off the popup
  window and have it disappear much like a popup menu

rebase/merge by hasufell, codebase by Brian Bidulock

Conflicts:
	data/popup_window-gtk2.xml
	src/main.c
Port the previous changes to the gtk3/gtk2 codebase

Also reinstate the old behavior of not closing the
popup window if you click anywhere inside.