Fix: add provider ABI compatibility check

Fix: add provider ABI compatibility check

There is not much we can do for this compatibility bug in lttng-ust 2.0
and 2.1 (already stable). Adding this check so that starting with
lttng-ust 2.2, when liblttng-ust encounters a probe provider with a
provider version major number higher than it supports, it will reject
it.

Fixes #502

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