Remove vtracelog and vtracef from v0 compat API

vtracelog and vtracef were introduced between lttng-ust 2.12 and 2.13
(not released yet). They are replaced by lttng_ust_vtracelog and
lttng_ust_vtracef in the v1 API, newly introduced in lttng-ust 2.13.

Therefore, there is no need to expose a v0 compat API for the vtracelog
and vtracef macros which were never officially part of any release
other than the 2.13 release candidates.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I96cfed7d6c211d24017bfd33cd8d8c5a7087d78f