PKGBUILD{,-git} improvements

Hello,

Using the rcm-git package from the AUR has always had an issue for me where it would never record its version properly, e.g. every time I would run pacaur -Syu an update would appear for rcm, and would subsequently be fetched, built, and rejected by pacman for being already installed. This fixes that for me, as well as gets rid of two ./configure warnings and makes it more in line with PKGBUILD guidelines. More detailed changes are in the commit message (although that was the gist of it).