Add "or", "and" and "not" as synonyms to "&&", "||" and "!".

From this discussion:
https://groups.google.com/forum/#!topic/osl-dev/nds648OuPvM

To clarify, this works fine:
unary_op
        : '-'                           { $$ = ASTNode::Sub; }
        | '+'                           { $$ = ASTNode::Add; }
        | '!'                           { $$ = ASTNode::Not; }
        | NOT_OP                        { $$ = ASTNode::Not; }
        | '~'                           { $$ = ASTNode::Compl; }
        ;