minor cleanups ...

- use for loops instead of while loops for basic list traversals
- only calculate word length one time in CLI complete functions
- use calloc instead of malloc + memset
- remove some unnecessary casts
- formatting tweaks 


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7618 65c4cc65-6c06-0410-ace0-fbb531ad65f3