Declare functions in utilties.c as INTERNAL_API

Fixes link failures on Win32

Change-Id: I90b19bea9b9b326e3ea8299e194a8f5ba963f9a5
Reviewed-on: http://review.couchbase.org/35884
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>