Improve GwtAstBuilder output when stack emulation is enabled.

Fixes a couple of places where GwtAstBuilder output is significantly different from the current output.

http://gwt-code-reviews.appspot.com/1460801/


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10361 8db76d5a-ed1c-0410-87a9-c151d255dfc7