Fix: missing Tracepoint prototype checking due to bogus merge

Backport of the following commit:

commit 6633b022a8e6ef247af926919b493284308f7883
Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date:   Fri Apr 17 16:35:35 2015 -0400

    Fix: check that class and instance prototype match

accidently disabled Tracepoint prototype checking by removing
the #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) required
to perform prototype checking between kernel and lttng-modules.
This issue was introduced in 2.6.1, only in the stable-2.6 branch.

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