Add some HISTORY sections to manpages

environ(7) was in AT&T Version 7
ac(8): Add a HISTORY section
sa(8): Add a HISTORY section
sqrt(3): Add the actual sqrt function to the HISTORY section

Obtained from: OpenBSD

Submitted by: gbergling@gmail.com
Approved by: bcr@(mentor)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D23693