MFC r318718,r318719,r318720,r318721:

r318718:

rctl_add_rule(2): fix manlint warnings

• Fix commas (either missing or misused) after .Nm entries in SYNOPSIS

r318719:

open(2): fix manlint warnings

• Sort SEE ALSO .Xr entries.
• Sort sections (HISTORY comes after STANDARDS).

r318720:

ptrace(2): clean up trailing whitespace

r318721:

kill(2): add missing section for sysctl(9)