libc: Add HISTORY sections to the manual pages

[gbe]

Summary

Add various HISTORY sections to the libc manual pages.

Obtained from: OpenBSD
MFC after: 2 weeks

Test Plan

mandoc output review and 'mandoc -Tlint' checks

[pauamma_gundo.com]

Summary needs s/sections the/sections to the/ before it ends up in the commit message

lib/libc/compat-43/sigvec.2

346–347

Given it's a wrapper now, shouldn't it be in section 3, like alarm(3) is?

lib/libc/db/man/dbm.3

227

When did dbm_clearerr, dbm_close, dbm_dirfno, dbm_error, and dbm_open appear?

May want to mention when the dbm_ prefix appeared too.

lib/libc/gen/setjmp.3

173

When did the others appear?

lib/libc/locale/ctype.3

152

What about the other functions? Also, when did the macro+function dual implementation come to be? I vaguely remember they were only macros at first.

lib/libc/stdio/ferror.3

132

When did the _unlocked versions appear?

[gbe]

@pauamma_gundo.com good questions, I do some research in the next couple of days.