call-channel: correct handle type
call-channel: call functions with correct arguments

We need more casts here and there to keep gcc happy (and we should).
call-channel: call close with the correct first argument
call-channel: remove unused variable
Revert "Use dbus_props_class from TpBaseChannelClass"

This reverts commit 22f89e6c26e080855201ea3ea1a0b8a8c6b906b5.