on the assumption that the normal armours are in ascending order by AC, from ARM_ROBE to ARM_PLATE_MAIL, so it seems okay to use that for now.
git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8903 c06c8d41-db1a-0410-9941-cceddc491573
WU3E44CEYAC6TWW7M62DXXEJGZO4VJ5TOJALOLAQUNHJGCICWTPAC
// Medium-level armours.
const armour_type medarmours[] = { ARM_ROBE, ARM_LEATHER_ARMOUR,
ARM_RING_MAIL, ARM_SCALE_MAIL,
ARM_CHAIN_MAIL, ARM_SPLINT_MAIL,
ARM_BANDED_MAIL, ARM_PLATE_MAIL };
armtype = RANDOM_ELEMENT(medarmours);
// Medium-level armours, up to plate mail.
armtype = ARM_ROBE + random2(8);