[antlr-interest] finished AST construction for tree grammars

[Terence Parr]

heh heh heh...cool stuff.

Will have to wait for 3.1 release, but works.  I may push a build.

http://www.antlr.org/wiki/display/ANTLR3/2007/07/27/Finished+tree 
+grammar+AST+construction

Next up: import for grammars.

Ter