Import warning flags and tap from Babeltrace

Since we are going to use this code in Babeltrace, lttng-tools, and
perhaps other projects, I think it would be useful to use warning flags
at least as strict here as we do in these other projects, so we don't
have bad surprises when importing the code there.

Start by importing the warning flag checking system from Babeltrace, and
the list of warning flags used there.

Import the tap code as well, since the current tap code would generate
some errors with the new warning flags.

Change-Id: I86bf5a18bcbce35b887d3ef3285d5566b3f7c69f
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>