Trigger checkpointing from within the application

[Matthew Dillon]

    HEAD now has the checkpointing code fully integrated, including syscall
    and signal support, and manual pages which describe its operation.

    See sys_checkpoint(2) and checkpt(1) for details.

    NOTE: A full buildworld and buildkernel is required because these commits
    have added a new system call.  An Incremental build will not work, sorry.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>