Support ANSI SQL double quotes

[dumblob]

There was a pull request https://github.com/dumblob/mysql2sqlite/pull/4 trying to add support for double quotes, but in a very dangerous way and also without supporting nested double quotes (i.e. escaping of double quotes).

It would be nice to implement a tiny parsing function in AWK which would first split the string into an array, find all the occurences, delete them and then join the array again together to build a string for returning.

I'm currently out of time, so volunteers are even more welcome!