Replace word repetitions in `t`.

def replace_wrep(t:str) -> str:
    "Replace word repetitions in `t`."
    def _replace_wrep(m:Collection[str]) -> str:
        c,cc = m.groups()
        return f' {TK_WREP} {len(cc.split())+1} {c} '
    re_wrep = re.compile(r'(\b\w+\W+)(\1{3,})')
    return re_wrep.sub(_replace_wrep, t)