Enhancement: Switched to new asterisk refcount debugging method. Used static declaration for ref_count_debug file and only open and close it once per module load/unload cycle. Copied their refcounter.py script to contrib directory.

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5745 43c1dc8c-776e-4df2-8ef1-6e829299be21