pwd_mkdb: retire legacy v3 db support (-l option)

[emaste]

Summary

pwd_mkdb has emitted v4 password database records since 2003 (rS113596) in addition to v3, and as of rS283981 by default it emitted only v4. As described in rS283981, retire the -l legacy option.

Additionally, set the db hash to be in network byte order (big-endian) as with other integers in the database. The db(3) functions work with a hash of either endianness. Using a fixed endianness allows us to create a password database that's reproducible regardless of host endianness.

The -B and -L options were originally added to set the endianness of v3 records emitted by pwd_mkdb, but they also set the db hash endiannes and so have been retained temporarily.

Mentioned on the FreeBSD-Current and FreeBSD-Stable lists
https://lists.freebsd.org/pipermail/freebsd-stable/2018-April/088782.html

[emaste]

usr.sbin/pwd_mkdb/pwd_mkdb.8

31

Bump .Dd upon commit

usr.sbin/pwd_mkdb/pwd_mkdb.c

129

Will add a deprecation warning in B and L cases.

[emaste]

Thanks for review. My plan:

• commit the change to default to BIG_ENDIAN hashes (rS332902)
• merge deprecation notice in the program, in man page, and the rS332902 BIG_ENDIAN change to stable/11 in the next few of days (with Relnotes: yes)
• commit this change (additionally with deprecation notice in -B / -L) to HEAD (with Relnotes: yes)
• remove -B and -L in a few months (with Relnotes: yes)