Support Plover-specific control words without ignored groups

For control words like `\cxplvrcancel` or `\cxplvrrtfcw` that don't have anything coming after them that might be interpreted as content, allow them to be included in the rest of the translation code without being in an ignored group.

For example: `{\*\cxplvrortho}\cxds ish` may be written simply as `\cxplvrortho\cxds ish`.
