MFC r318715,r318717,r318718,r318719,r318720,r318721:

r318715:

_umtx_op(2): fix minor manlint issues

• Sort .Xr entries in SEE ALSO section.
• Sort SEE ALSO and STANDARDS sections properly, in terms of the entire document.

r318717:

cap_enter(2): fix manlint issues

• Sort SEE ALSO section appropriately.
• Correct section for sysctl(9).

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)