Added a new decorator function in the "lldb" module that can register a...

Added a new decorator function in the "lldb" module that can register a command automatically. We have just a few kinks to work out for the Xcode workflow and we will be ready to switch over to using this. To use this, you can decorate your python function as:

@lldb.command("new_command", "Documentation string for new_command...")
def new_command(debugger, command, result, dict):
    ....
    
No more need to register your command in the __lldb_init_module function!

llvm-svn: 184274