[antlr-interest] Fixed meaning of . wildcard in tree grammar

[Terence Parr]

Howdy.  So, wildcard '.' in tree grammar means node OR subtree  
officially now (and correctly).  I fixed a number of code gen issues  
with '.' during AST construction in tree grammars.  Because it can be  
a subtree, ^(. foo) is invalid.  Fortunately, the root says what to do  
and you would rarely ask for any root.  if wanted it, a simple DFS  
would suffice rather than a pattern match.

Fixed these bugs (for v3.2):

http://www.antlr.org:8888/browse/ANTLR-248
http://www.antlr.org:8888/browse/ANTLR-344

Added a bunch of unit tests.

More testing then a daily release soon.

Ter