WindowsUtils.kill() fix

On Windows 8 the kill() function did not correctly locate
the process in the list. There were two issues:

* The executable name in the regexp was duplicated. This patch changed
  the iteration over the arguments to not include the executable again.

* If the process was started without using .exe in the name kill()
  could not find it as the regexp did not have the .exe there. This patch
  adds .exe if not already present as an optional match.

Signed-off-by: Andreas Tolf Tolfsen <andreastt@opera.com>