JDK 9 RFR(m): 8150488: Scanner.findAll() can return infinite stream if regex matches zero chars

[Stuart Marks]

Hi all,

Please review this fix [1] for JDK-8150488 [2] to prevent Scanner.findAll() from 
returning an infinite stream of zero-length matches in certain cases.

This was previously an issue that simply documented this limitation. In the 
review for that issue [3], Timo K convinced me that this behavior is actually a 
bug, and Sherman convinced me that it's worth fixing in 9 since findAll() is a 
newly introduced API. Also, thanks to Sherman for providing an initial 
implementation.

Thanks,

s'marks

[1] Webrev: http://cr.openjdk.java.net/~smarks/reviews/8150488/webrev.0/

[2] Bug: https://bugs.openjdk.java.net/browse/JDK-8150488

[3] Previous review threads:

     http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-March/046995.html
     http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-April/047055.html