Fix build problem on Debian with R17

The Erlang packages for Debian installs erl_nif.h to
/usr/include (which is in the default compiler search path),
but erl_nif.h tries to include erl_native_features_config.h which
isn't installed there, but in /usr/lib/erlang/usr/include

Change-Id: I1df67c838f4fccaecfa14b6be407cf099c22ec03
Reviewed-on: http://review.couchbase.org/36265
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>