Turning on javac lint warnings when building Java sources in jdk 8 repo

[Joe Darcy]

Hello,

Over the last few months, over on core-libs-dev there have been various 
clean up efforts concerning the Java code in the JDK 8 "jdk" repo, 
resolving both javac lint and doclint warnings.

With these clean ups in place, I think it is time for selected 
categories of javac lint warnings to be enabled during the build under 
-Werror. That is, for lint categories that have been scrubbed, the build 
should be reconfigured so that reintroducing such a warning is a build 
error. (Under the old build, different packages could use different 
javac command line options. With the new build, all the Java code is 
compiled under the same options so the full build was reduced to the 
least restrictive javac lint setting.)

As additional warning categories are resolved, the set of enabled lint 
categories could be expanded, potentially including doclint categories too.

Cheers,

-Joe

[1] http://mail.openjdk.java.net/pipermail/build-dev/2013-August/009806.html