niti: add extern method atof

Signed-off-by: Jean Privat <jean@pryen.org>
tests: add a basic interpretation

Signed-off-by: Jean Privat <jean@pryen.org>
tests: add post-args execution

Signed-off-by: Jean Privat <jean@pryen.org>
tests: add post-args to nitc

Signed-off-by: Jean Privat <jean@pryen.org>
tests: add args to nitg.nit

Signed-off-by: Jean Privat <jean@pryen.org>
oldmm: add MMtype#has_formal

Signed-off-by: Jean Privat <jean@pryen.org>
nitc: do not warn on isa related on formal

Signed-off-by: Jean Privat <jean@pryen.org>
tests: add test_string2.nit

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