inet.4 tcp.4 udp.4: Replace *CTL_* OID macro names with sysctls

[karels]

Summary

Older sysctls with constant OID macros were identified with those
in inet.4, tcp.4, and udp.4; newer sysctls with automatic numbering
were identified by sysctl names. No one remembers the OID macros,
or knows what they are; sysctls are always done by name now, usually
via sysctl(8).

Replace the OID macro names with sysctl names so that there is one
uniform identifier type; sysctl names were previously in parens.
Make the formatting a little more consistent in this area. In inet.4
and udp.4, move the "ip." or "udp." prefix from each entry into the
top-level name at the start of the section, as they are all the same.

Test Plan

tested with mandoc

[rpokala]

share/man/man4/inet.4

173

I think this paragraph reads more clearly like this:

In addition to the variables supported by the transport protocols in
.Va net.inet
(for which the respective manual pages may be consulted),
there are a number of general variables implemented in the
.Va net.inet.ip
branch of the
.Xr sysctl 3
MIB.
The following general variables are defined:

[karels]

Replace intro to sysctl section in inet.4 with suggested text.

[karels]

share/man/man4/inet.4

173

Thanks, that is a definite improvement.

[rpokala]

LGTM.

share/man/man4/inet.4

173

Thanks!