Fix sccp reload for buttonconfig parsing (detect reordering of buttons / detect change of buttondefinition) (Reported by Andy Bradford / Alena Juk / #188)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4758 43c1dc8c-776e-4df2-8ef1-6e829299be21