This patch just moves the IAX2 source and header files into a separate iax2
sub-directory in the channels directory, similar to how the sip source files are
structured.
The only thing that was added was an #ifndef to protect provision.h from multiple
inclusion.
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@380433 65c4cc65-6c06-0410-ace0-fbb531ad65f3