vectorize string-escape with NEON

[sebpop]

On this benchmark:

function simple_string_escape() {
    $a = "test'asd'asd'' asd\'\"asdfasdf";
    for($i=0; $i<512; $i++) {
        $a .= chr($i%256);
    }
    for ($i = 0; $i < 100000; $i++) {
        if ($a === stripslashes(addslashes($a)))
            $a .= chr($i%256);
        else {
            echo "error at i=".$i."\n";
            return;
        }
    }
}

the execution time goes from 21.619s to 8.139s (165% speedup) on an A1 Graviton instance.

When removing the characters that need escaping, i.e., this benchmark:

function simple_string() {
  $a = "testasdasd asdasdfasdf";
  for ($i = 0; $i < 10000; $i++) {
      if ($a === stripslashes(addslashes($a)))
          $a .= "test dedeasdf";
      else {
          echo "error at i=".$i."\n";
          return;
      }
  }
}

the execution time goes from 2.932s down to 0.516s (468% speedup) on an A1 Graviton instance.

[dstogov]

Merged as af76396