Bug fix: Issue #36: Chromium window painting problems

More descriptions on issue #36.

- Listens ShapeNotify event to get around the Chromium window painting
  issues.

- Adds dependency on X Shape extension.

- Adds a few functions for convenience, so a bit code clean up.

- Better event debug support, adds restack_win() debug.

Makefile

@@ -4,7 +4,7 @@ PREFIX ?= /usr
 BINDIR ?= $(PREFIX)/bin
 MANDIR ?= $(PREFIX)/share/man/man1
 
-PACKAGES = x11 xcomposite xfixes xdamage xrender
+PACKAGES = x11 xcomposite xfixes xdamage xrender xext
 LIBS = $(shell pkg-config --libs $(PACKAGES)) -lm
 INCS = $(shell pkg-config --cflags $(PACKAGES))
 CFLAGS += -Wall