file: fix diname behavior when result is "/"

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

Signed-off-by: Jean Privat <jean@pryen.org>
rename 'package' to 'module'

Signed-off-by: Jean Privat <jean@pryen.org>
lexer: distinguish keywords 'package' and 'module'

Signed-off-by: Jean Privat <jean@pryen.org>
file: add String::chdir

Signed-off-by: Jean Privat <jean@pryen.org>
niti: implements file_chdir and file_getcwd

Signed-off-by: Jean Privat <jean@pryen.org>
niti: add option -m for mix-in modules

Signed-off-by: Jean Privat <jean@pryen.org>
tests: test -m with nit.nit

Signed-off-by: Jean Privat <jean@pryen.org>
nitg: add option -m for mix-in modules

because super is not yet polymorph in nitg-s, the test nitg_args6 is
not saved

Signed-off-by: Jean Privat <jean@pryen.org>
Merge branch 'chdir'
Merge branch 'mixinmodule'