Enhancement: Added sched_add_ref/sched_del_ref/sched_replace_ref wrapper functions

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5729 43c1dc8c-776e-4df2-8ef1-6e829299be21
Enhancement: Remove sccp_sched_del / sccp_sched_add functions in favor of the PBX() versions

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5730 43c1dc8c-776e-4df2-8ef1-6e829299be21
Fix: CS_AST_CONTROL_INCOMPLETE handling in regards to digittimeout

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5731 43c1dc8c-776e-4df2-8ef1-6e829299be21