RFR 8065998: Avoid use of _ as a one-character identifier

[Jan Lahoda]

Hi,

In a preparation for JDK-8061549, I'd like to rename all uses of '_' as 
a one-character identifier in the jaxp and jdk repositories. All the 
uses I was able to find are in tests, and the identifier is used as a 
name of a catch parameter. The proposed new name is "ignore", but if a 
different name would be more appropriate, I'll be happy to use it.

Webrev for the jaxp repository:
http://cr.openjdk.java.net/~jlahoda/8065998/webrev.00/jaxp/

Webrev for the jdk repository:
http://cr.openjdk.java.net/~jlahoda/8065998/webrev.00/jdk/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8065998

Any comments are appreciated.

Thanks,
     Jan