Function argument_boolean 

pub fn argument_boolean(argument: &PragmaArgument) -> bool

Reads a pragma argument as the boolean SQLite accepts.

SQLite reads on, yes and true as one, a number that starts with a digit as itself, and everything else as zero, which is why PRAGMA foreign_keys = maybe and PRAGMA foreign_keys = -1 turn them off. See sqlite_boolean.

@param argument - the argument as the parser produced it