Function runtime_text_reverse 

pub extern "C" fn runtime_text_reverse(
    dest: i64,
    src: i64,
    off: i64,
    len: i64,
)

Reverse UTF-8 text. Matches text-2.1.2 _hs_text_reverse(dst0, src0, off, len).

Reads len bytes from src + off, writes reversed codepoints starting at dst.