Apply MethodCase config to Rectangle::center

[ephphatha]

The bit that makes the amiga build break 🙃

[StephenCWills]

Looks like -O3 fails, but -O2 succeeds. I tried to see if I could pinpoint which optimization is causing problems, but I'm completely stumped. According to the output of -Q --help=optimizers, -O3 is equivalent to -O2 -fgcse-after-reload -finline-functions -fipa-cp-clone -fpredictive-commoning -fsplit-paths -ftree-loop-distribute-patterns -ftree-partial-pre -funswitch-loops -fvect-cost-model=dynamic, but the error does not occur unless I use -O3. 🤷