Support "excludePackages" as a way to logically exclude packages from API checking whose source files must be available to create a consistent TypeOracle.

Review by: amitmanjhi (postmortem)


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@3359 8db76d5a-ed1c-0410-87a9-c151d255dfc7