Add ZAP_TON_* (taken from Q931.h, drop Q921.h and Q931.h include from openzap.h and fixup all users of the old Q931_TON_ enum values)

git-svn-id: http://svn.openzap.org/svn/openzap/trunk@707 a93c3328-9c30-0410-af19-c9cd2b2d52af