util-mem - WIN32 case identical to !WIN32 case

Remove the #ifdef for WIN32, since both cases have the same function, differing
only in using "a" or "(a)" in the syntax.

This is just code clean up.

Passes all regression tests:
https://buildbot.suricata-ids.org/builders/ken-tilera/builds/78
https://buildbot.suricata-ids.org/builders/ken-tilera-pcap/builds/15