Add workaround for memory leak in std::regex
Add workaround for memory leak in std::regex

There is a memory leak in std::regex on our valgrind commit
builders. This memory leak isn't something we care about as
we only create a single instance of it in the lifetime of
the program. Instead of having to modify the suppression
list passed to valgrind we can just use a unique pointer
in this case as we don't utilize the regexp when running
with valgrind.

Change-Id: If7c6bb46cb4f892e892f4836b3bd2430be204cf5
Reviewed-on: http://review.couchbase.org/71173
Reviewed-by: Jim Walker <1cd02e31b43620d7c664e038ca42a060d61727b9@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,couchbase/memcached,daverigby/kv_engine,couchbase/memcached,daverigby/memcached,couchbase/memcached,daverigby/memcached,couchbase/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/kv_engine,daverigby/memcached