MFC r256695:
- Add relative specification in expiration time.
- Add proto3 option for RTF_PROTO3.
- Use %lu for members of struct rt_metrics.

Merge r260524,r260540

r260524:
Add -4/-6 shorthand for -finet/-finet6 in route(8) and netstat(8).

r260540:
Bump dates in nestat(1) and route(8) man pages.
Fix several small errors introduced by r260524.

Suggested by: glebius

MFC r256695:
- Add relative specification in expiration time.
- Add proto3 option for RTF_PROTO3.
- Use %lu for members of struct rt_metrics.

Merge r260524,r260540

r260524:
Add -4/-6 shorthand for -finet/-finet6 in route(8) and netstat(8).

r260540:
Bump dates in nestat(1) and route(8) man pages.
Fix several small errors introduced by r260524.

Suggested by: glebius