Tweaks to make JDT use less memory.

- Changed options to not build javadoc, suppress warnings, etc.
- Shadowing SourceTypeBinding to use our lightweight HashMap.
- Jsni collection was pinning entire compilation unit source.

Review by: spoon

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5162 8db76d5a-ed1c-0410-87a9-c151d255dfc7