Tune the installed manual pages.

Tune the installed manual pages.

This commit slightly improves the formatting of the manuals.  My
OpenBSD machine uses mandoc(1) to format manuals.  I check the manuals
with `mandoc -T lint` and fix most of the warnings.  I also make
other changes where mandoc didn't warn me.

roff(7) says, "Each sentence should terminate at the end of an input
line," but we often forgot this rule.  I insert some newlines after
sentences that had ended mid-line.

roff(7) also says that blank lines "are only permitted within literal
contexts."  I delete blank lines.  This removes some extra blank lines
from mandoc's output.  If I do want a blank line in the output, I call
".sp 1" to make it in man(7).  If I want a blank line in the source,
but not the output, I put a plain dot "." so roff ignores it.

Hyphens used for command-line options, like \-a, should be escaped by
a backslash.  I insert a few missing backslashes.

mandoc warns if the date in .TH doesn't look like a date.  Our manuals
had a missing date or the RCS keyword "$Revision$".  Git doesn't
expand RCS keywords.  I put in today's date, 2017-01-18.

Some manuals used tab characters in filled mode.  That doesn't work.
I use .nf to turn off filled mode, or I use .IP in man(7) to make the
indentation without a tab character.

ack(1) defined a macro .SB but never used it, so I delete the
definition.  I also remove a call to the missing macro .RF.

mandoc warns about empty paragraphs.  I deleted them.  mandoc also
warned about these macro pairs in anm(1):

    .SM
    .B text

The .SM did nothing because the .B text is on a different line.  I
changed each pair to .SB for small bold text.

I make a few other small changes.