re-implement ast_separate_app_args with clearer code and in a way that doesn't...

re-implement ast_separate_app_args with clearer code and in a way that doesn't fail with certain combinations of array size and delimiter count
add doxygen docs for ast_separate_app_args


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@5566 65c4cc65-6c06-0410-ace0-fbb531ad65f3