Enhancements to release.sh based on work done to generate-release.sh

- Parameterize out make
- Support OptionsNG
- Use shell built-ins for arithmetic instead of expr

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
More enhancements to improve release.sh

- Turn the checkout operations into functions
- Move the functions up to the top so they can be overridden
  by release.conf

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
Return ENETDOWN when the parent interface is down.

MFC after:	1 week
Fix WITHOUT_* and parameterizing make isn't necessary

Suggested-by: gjb
Signed-off-by: Garrett Cooper <yanegomi@gmail.com>