usr.sbin/ndp:
- Constify rtpref_str declaration
- Remove unused h_errno declaration
- Use time_t type for expire
- Use strlcpy to set static "?" value to ifname
- Rename local variable 's' to stop shadowing global definition
- Close socket used in pfx_flush()
- Use local variables for sock() in setdefif() and getdefif()
- Increase WARNS to 3