crash utility help pages

`crash> help`

`*`	`files`	`mach`	`repeat`	`timer`
`alias`	`foreach`	`mod`	`runq`	`tree`
`ascii`	`fuser`	`mount`	`search`	`union`
`bt`	`gdb`	`net`	`set`	`vm`
`btop`	`help`	`p`	`sig`	`vtop`
`dev`	`ipcs`	`ps`	`struct`	`waitq`
`dis`	`irq`	`pte`	`swap`	`whatis`
`eval`	`kmem`	`ptob`	`sym`	`wr`
`exit`	`list`	`ptov`	`sys`	`q`
`extend`	`log`	`rd`	`task`

`crash version: 7.0.0 gdb version: 7.6 For help on any command above, enter "help <command>". For help on input options, enter "help input". For help on output options, enter "help output". crash>`