flex_starts_z && cflex_starts_s && stem_ends_k
function retroflex_k(hash) {
    var stemh = hash.stem.replace(/क्$/, 'ह्');
    var stemz = hash.stem.replace(/क्$/,'ष्');
    var stemj = hash.stem.replace(/क्$/,'ज्');
    var stemc = hash.stem.replace(/क्$/,'च्');
    if (stemh == hash.stem && stemz == hash.stem  && stemj == hash.stem) return;
    hash.stems = [stemh, stemz, stemj, stemc];
    if (debug) log('mod: retroflex_k', hash.stems);
}