- conversion to allocation wrappers

- get rid of some compiler warnings due to usused variables and const-ification
- remove some unnecessary uses of malloc/strncpy/free and replace with ast_strdupa
(based on the patch from issue #6275)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@8408 65c4cc65-6c06-0410-ace0-fbb531ad65f3