File.createTempFile() sometimes hangs on the build system while trying to get an exclusive lock on a temp file.  This patch uses a custom method to create a temp file.

Patch by: jlabanca
Review by: fabbott



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6023 8db76d5a-ed1c-0410-87a9-c151d255dfc7