Make the :sym following a token identifer optional
Make the :sym following a token identifer optional

The previous regex had a bug where it would only consume an identifier
following the token/regex/rule keyword if it ended in :sym.  This caused
some token names to be improperly highlighted

kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,dbrgn/pygments-mirror,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,dbrgn/pygments-mirror,kirbyfan64/pygments-unofficial,dbrgn/pygments-mirror,dbrgn/pygments-mirror