up to v20130603 (June 3, 2013)

- Produce smaller code for boolean conditional expressions.
- Better type checking for classes that implement or extend generic types.
- More accurate attaching of JSDoc to AST nodes.
- Allow collapse properties to collapse simple global aliases.
- New CheckEventfulObjectDisposal pass for finding memory leaks in JS programs.
- Change RescopeGlobalSymbols to not rewrite variables that do not cross JSModules.
- Fix  issue 965,  issue 987,  issue 994,  issue 1002,  issue 1006,  issue 1008.