Add symlink cmake/configure => configure.pl

This will hopefully let users use "configure" as normal, while also
allowing for the coexistence of autotools' configure (if we decide to
package it).

Change-Id: Ib6a354a1f4eec8151fb2823d88c5a029cc6c7d8f
Reviewed-on: http://review.couchbase.org/43694
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>