ast: remove classes AAtArg and make them simple AExpr

Signed-off-by: Jean Privat <jean@pryen.org>
parser: add tuples

Signed-off-by: Jean Privat <jean@pryen.org>
parser: regenerate

Signed-off-by: Jean Privat <jean@pryen.org>
grammar: add qmethid for qualified methid id

Signed-off-by: Jean Privat <jean@pryen.org>
ast: accept methodid in at_args

Signed-off-by: Jean Privat <jean@pryen.org>
parser: generalise Prod::collect_text

Signed-off-by: Jean Privat <jean@pryen.org>
annotation: `as_id` works with operators and setters

Signed-off-by: Jean Privat <jean@pryen.org>
regen-parser