cfg_lexer_include(): Check return value from tilde expand
cfg_lexer_include(): Check return value from tilde expand

- Streamline code paths for cfg_searchpath() and cfg_tilde_expand()
- Add translation _("") of error messages in case of fail
- Add missing check for NULL return value of cfg_tilde_expand()

Signed-off-by: Joachim Nilsson <583c295fd7602c168ad814279bbc3894ba65f5d6@gmail.com>

westermo/libconfuse,westermo/libconfuse,troglobit/libconfuse,troglobit/libconfuse,peda-r/libconfuse,peda-r/libconfuse,martinh/libconfuse,martinh/libconfuse