Crossgrading from Fedora 22 i686 to x86_64

I’ve always upgraded my Fedora laptop incrementally using the recommended tools (yum, preupgrade, fedup). For this reason, my initial decision to install i686 Fedora (back when 32-bit compatibility was important) has carried through, and I’ve always used i686 Fedora, even though the CPU supports x86_64. Recently I wanted to try out Mezzano in a virtual …