Allow to compile phantomjs without touch events in webkit

Added missing #if ENABLE(TOUCH_EVENTS)
for generated/JSDocument.* files

issue: http://code.google.com/p/phantomjs/issues/detail?id=375

Just compile with ./build.sh --qt-config "-D ENABLE_TOUCH_EVENTS=0"

Please cherry-pick this change to 1.8 branch for upcoming bug fix release, thx