This is a combination new feature/bug fix for app_chanspy.

New feature: Add the 'e' option, which takes as an argument a list of
interfaces separated by colons. This way, you will only be able to spy
on this limited list of interfaces.

Bug fix: change some pointer checks to ast_strlen_zero so that spying
would work properly even if no channel was specified as the first argument
to chanspy.


(closes issue #10072)
Reported by: xmarksthespot
Patches:
      bugfix+newfeature10072patchtotrunkrev102726.diff uploaded by xmarksthespot (license 16)
	  Tested by: xmarksthespot, mvanbaak



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@102933 65c4cc65-6c06-0410-ace0-fbb531ad65f3