Expand @CENTER@ to include other @-codes

Currently @CENTER@ ignores other @-codes.

Per IRC conversation, it may be possible to fix @CENTER@ to also parse other @c-codes.

The problem with this approach is that @CENTER@ doesn't/can't accurately know the expanded size of the string with @-codes (if they're variable width).

Would using the 'C' @-code format modifier work better? https://wiki.synchro.net/custom:atcodes#format_modifiers

closed with commit 961f1f58

mentioned in commit 961f1f58

mentioned in commit 0178043e