Do a deep copy of file and function strings to avoid a potential crash when

modules are unloaded.

(closes issue #12780)
Reported by: ys
Patches:
      logger.diff uploaded by ys (license 281)
	  -- modified by me for coding guidelines


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@119892 65c4cc65-6c06-0410-ace0-fbb531ad65f3