Make sure tab-completion works even when we have typed a fully

matching word (e.g. "sip<TAB>"); this is implemented by this one-line change

-               for (;; dst++, src += n) {
+               for (;src < argindex; dst++, src += n) {

However this code is not exactly trivial to understand, so
i am also adding some comments to help figuring out what it does.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@48408 65c4cc65-6c06-0410-ace0-fbb531ad65f3