[antlr-interest] set max number of characters in a string literal

[Olya Krachina]

Hello, 
I am working on a lexer and i was wondering how i could set a max limit on the
number of characters that make up a string literal, i.e. it is valid when there
are n (let's say n = 20) or less chars. I tried setting lookahead to 20 (options
k = 20) but it did not have any effect. I am using antlr 2.7. 

thanks in advance for any ideas on this,
Olya