various cleanups, including ...

- Create an astmm_log() macro that logs the same message to both stderr as well
  as the mmlog file if it is open instead of duplicating the code everywhere.
- Use for loops for list traversals instead of while loops
- reduce nesting
- ensure locking isn't put around more than is necessary
- localize a struct definition
- change the limit of the path to the mmlog to PATH_MAX instead of 80


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@40780 65c4cc65-6c06-0410-ace0-fbb531ad65f3