Added sample for more precise change checking to sccp_config_parse_codec_preferences. Clarified that sccp_parse_allow_disallow returns the number of errors that occurred during parsing.

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4824 43c1dc8c-776e-4df2-8ef1-6e829299be21