boot.rb: Improve configuration reloading callbacks
signal.rb: Revert at_exit shutdown handler

Under jruby, at_exit() is not being called imediatelly upon exit(-1)'ing from signal trap.
Instead, it takes ~30 secs for this handler to be eventually invoked.
Bump version to 0.6.3
Merge pull request #1 from madvertise/4145_update_ext_and_shared_gems

4145 update ext and shared gems