parser: _location it no more nullable, so use isset for magic when needed

Signed-off-by: Jean Privat <jean@pryen.org>
parser: remove manual old-style attributes

Signed-off-by: Jean Privat <jean@pryen.org>
parser: batch remove old style attribute

~~~
sed -i 's/var _n\(.*: nullable.*\)/var n\1 is writable/' parser/parser_nodes.nit
sed -i 's/var _n\(.*\)/var n\1 is writable, noinit/' parser/parser_nodes.nit
sed -i '/fun n_\(.*\)/d' parser/parser_nodes.nit
sed -i '/init do end/d' parser/parser_nodes.nit
~~~

Signed-off-by: Jean Privat <jean@pryen.org>
parser: remove old-style attributes in xss

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

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update sav because ligne changes in lib

Signed-off-by: Jean Privat <jean@pryen.org>
pep8analysis: update and remove old-style attributes

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