[antlr-interest] we can do push/pop error stuff for 4%

[Terence Parr]

Hi, so implemented my own stack and it's way faster.

parse+lex 6261ms	using java.util.Stack
parse+lex 3710ms	using no push/pop at all
parse+lex 3860ms	using my own stack

Given that lexing is like 1500ms, adding good error handling,  
recovery only costs us about 150ms or 4% cpu speed.  I'll leave in,  
but make it to use my stack.  Wow.  My stack costs 150ms vs 2551ms  
for java.util.Stack.  What the hell is it doing?  ick.

Ter