/**
* shoves back characters into the input of the <code>DfaRun</code>. This method simply applies
* {@link TextStore#drain TextStore.drain()} to the input of <code>this</code>. Consequently,
* <code>start</code> may be negative to indicate a suffix of <code>ts</code> to be pushed back.
*/
public void unskip(TextStore ts, int start) {
ts.drain(in, start);
}
