Use -DREVISION instead of -DSCCP_REVISION

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5167 43c1dc8c-776e-4df2-8ef1-6e829299be21
Fix checking if channel_retain actuall found a channel, instead of overwriting channel with NULL in sccp_line_removeChannel / sccp_line_addChannel

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5168 43c1dc8c-776e-4df2-8ef1-6e829299be21