RFR JDK-8176029: Linebreak matcher is not equivalent to the pattern as stated in javadoc

[Xueming Shen]

Hi,

Please help review the change for JDK-8176029

issue: https://bugs.openjdk.java.net/browse/JDK-8176029
webrev: http://cr.openjdk.java.net/~sherman/8176029/webrev

It appears the API doc for \R is correct, instead the implementation is 
buggy when
dealing with sequence "\r\n" (u+000du+000a). The existing implementation 
fails to
backtrack to match \r and then next.match() when the attempt \r\n + 
next.match()
failed. As a simple obvious sample both following should return true. 
The existing
implementation returns false for the second.

     "\r\n".match("\\R")
     "\r\n".match("\\R\\n")

Thanks,
Sherman