_tp_connection_ref_handles, tp_connection_unref_handles: simplify allocation of data structures
_tp_connection_ref_handles, tp_connection_unref_handles: simplify allocation of data structures

_tp_connection_init_handle_refs now preallocates some of the data
structures, so we can just assert that they're good rather than allocating
them lazily.

Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib