WASHINGTON (Reuters) - A "bunker buster" bomb with more than 10 times the explosive power of its predecessor is to be put into service by the United States next December, six months later than previously scheduled, the Defense Department told Reuters on Friday. The deployment's timing may help shape new calculations in long standoffs with Iran and North Korea over their nuclear programs, much of which are believed to be underground to avoid detection and enhance their chances of surviving an attack. "Funding delays and enhancements to the planned test schedule have pushed the capability availability date to December 2010,"...