Lie to Java about which window manager it is using

Without this hook, swing shows blank grey screen when using jdk7. The solution
is found here:
http://www.haskell.org/haskellwiki/Xmonad/Frequently_asked_questions#Using_SetWMName
The first (preferred) solution where it sets the environment variable
_JAVA_AWT_WM_NONREPARENTING=1 did not fix the issue. icedtea-bin:7 and
oracle-jdk-bin:1.7.0.60 has been used but neither fixed this issue until
setting this hook. This hook works for both JVM (current system VM is set to
icedtea-bin-7). JDK8 has not been tested.