Make libnewblue headers C++ friendly.

This CL adds extern "C" wrapping for exported headers so that the C++
consumers can include them without specifying extern "C" themselves.

BUG=chromium:840517
TEST=Build C++ client (newblued) without extern "C".

Change-Id: Ifa164bf274e39bb7fbf3380e76be8a069912f0aa
Reviewed-on: https://chromium-review.googlesource.com/1089920
Commit-Ready: Sonny Sasaka <sonnysasaka@chromium.org>
Tested-by: Sonny Sasaka <sonnysasaka@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
7 files changed