sysctl: Misc code cleanup

[freqlabs]

Summary

• Use defined SYS_SYSCTL names
• Use memcmp instead of explicit loop
• Use NULL instead of 0 for pointer value
• Use __FBSDID
• Reformat, improve comments in parse()

No functional changes.

Sponsored by: iXsystems, Inc.

[freqlabs]

Separated kern_sysctl changes to a different patch.
Use defined CTL_SYSCTL oid names.

[imp]

Modulo the blank line thing, this looks good. It's arguably two different commits, but it's so small splitting it further at this stage likely has little benefit.

sbin/sysctl/sysctl.c

368 ↗

(On Diff #78415)

Nit: in most of the tree we don't have a blank line separating the comment from the code like this. Here and below

[freqlabs]

In D26832#600476, @imp wrote:

Modulo the blank line thing, this looks good. It's arguably two different commits, but it's so small splitting it further at this stage likely has little benefit.

I have it as 5 separate commits in my git tree but putting up separate reviews for each one on phabricator is not practical. I plan to do one commit to svn as well to avoid confusing phabricator.

[freqlabs]

Removed blank lines following section comments.