function consumeEscape(css, start) {
	  var next = start;
	  var code = css.charCodeAt(next + 1);
	  if (unescapable[code]) ; else if (hex[code]) {
	    var hexDigits = 0;
	    // consume up to 6 hex chars
	    do {
	      next++;
	      hexDigits++;
	      code = css.charCodeAt(next + 1);
	    } while (hex[code] && hexDigits < 6);
	    // if fewer than 6 hex chars, a trailing space ends the escape
	    if (hexDigits < 6 && code === t.space) {
	      next++;
	    }
	  } else {
	    // the next char is part of the current word
	    next++;
	  }
	  return next;
	}
Returns the last index of the escape sequence
@param {string} css The string in which the sequence begins
@param {number} start The index into the string where escape character (`\`) occurs.