Conference can only be joined using an active call

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4401 43c1dc8c-776e-4df2-8ef1-6e829299be21
Re-enable conference debug log out put for Hide Conf List

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4402 43c1dc8c-776e-4df2-8ef1-6e829299be21
Remove unused function calls from sccp_conference.h

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4403 43c1dc8c-776e-4df2-8ef1-6e829299be21
_FORTIFY_SOURCE only enabled when optimizing (openSuSE 12.3) (fixes #72)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4404 43c1dc8c-776e-4df2-8ef1-6e829299be21