Function _toLOWER_utf8_flags 

pub unsafe fn _toLOWER_utf8_flags(
    my_perl: *mut PerlInterpreter,
    p: *const U8,
    e: *const U8,
    s: *mut U8,
    l: *mut STRLEN,
    f: bool,
) -> UV

thx shim for crate::_toLOWER_utf8_flags.