Added infrastructure to profile compiler memory usage.
- reporting memory usage at various points
- dumping the heap at various points
- logging changes to the Java AST

Also remove the printing of a JMethod's thrown exceptions; this will soon go away entirely.

Review by: spoon

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5147 8db76d5a-ed1c-0410-87a9-c151d255dfc7