full text search for words with a few specific chars

Hi,

I have a problem, and here it is:

when execute this:

select to_tsvector('simple', 'a.')

I god just one result: 'a' because "." is a "Space symbol"

So, my question is what is the best way to remove a few chars from a
space symbol list, for this (simple) dictionary or another (newly
created). I can not find system db, or a file where postgresql store
those symbols.

Hope that I was clear with question.

Thanks.