use more correct const char * for things that should not be modified.  This should also fix the switch_cpp.cpp changes from MODAPP-44.  More patches to follow up on this for a few more modules that will likely break with this commit.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6120 d0543943-73ff-0310-b7d9-9358b9ac24b2