Clean up standards(5), etc, eliminate legacy standards

[Garrett D'Amore]

standards(5) is a mess.

We would like to clean it up, and ideally eliminate the attempts to supply conformance for legacy standards. The legacy standards that we think no longer apply are:

• SVID3
• XPG3
• XPG4
• POSIX 90, 95

XPG4v2 / SUS is a standard from 1995. That's nearly 20 years ago! Its time to modernize. This leaves:

• SUS
• SUSv2
• SUSv3
• SUSv4

Which covers UNIX 95, UNIX 98, UNIX 03, and some future UNIX brand (UNIX13?)

Note we are proposing elimination of APIs. We should avoid breaking binary interfaces, although some command line programs may be changed (in the future.)

[Garrett D'Amore]

fixes #92 Need new confstr variables fixes #45 Clean up standards(5), etc, eliminate legacy standards

→ <<cset ce6d82876658>>

[Garrett D'Amore]

fixes #45 Clean up standards(5), etc, eliminate legacy standards (fix pkg)

→ <<cset 41ea5de17eb5>>