This fixes https://savannah.gnu.org/bugs/?51348

.
Reported-by: Henrik Karlsson <henrik.karlsson@pulsen.se>
Tested-by: John Wiersba <jrw32982@yahoo.com>

For the man page, encode them properly, and for the Info stuff,
just set the right document encoding.

This fixes https://savannah.gnu.org/bugs/?51369.

The comment marker is not «."» but «.\"», which requires three
backslashes to specify.  Also adjust the documentation.

Also, use proper mark-up for the examples.

This matches the style in the rest of the code.

This avoids some warnings when compiled with -pedantic:

    ISO C forbids comparison of ‘void *’ with function pointer
    ISO C forbids empty initializer braces

When blank_statusbar() has been called, make sure it is effective.

This fixes https://savannah.gnu.org/bugs/?51358.

(Well, redraw them when they're switched on, of course.)  Redraw
them so that they are shown correctly if their content changed.

This fixes https://savannah.gnu.org/bugs/?51356.
and fixes https://savannah.gnu.org/bugs/?51357.

The thing after a 'comment' directive is just a string, not the
name of a program nor a command.

When the active syntax contains a comment command that specifies the
empty string, this should override the default comment of "#" and
should disable the Meta-3 keystroke.

To achieve this, the comment string is now set by default to "#" for
all syntaxes, so that it will be set when no comment command is given
(including for the "none" syntax), and is unset only by explicitly
specifying «comment ""» in a syntax file.

This fixes https://savannah.gnu.org/bugs/?51355

.
Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

And rename a third variable, to match another in its style.

When also --nohelp is active and the terminal is so narrow that the
message that --constantshow displays on the bottom row does not fit,
this causes the cursor to be pushed "offscreen".  Some terminal
emulators don't handle this case correctly, and leave the cursor
in an invisible or mistaken position.  Compensate for this by
moving the cursor back to the start of the row.

This fixes https://savannah.gnu.org/bugs/?51335

.
Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

The extra variable is not needed, because when having read from
standard input, the filename will simply be empty.  It will not
be empty for any other file that was read.

The dash doesn't have to be the first non-option argument: it can
be anywhere among the filenames -- there can even be multiple ones
(but don't mention this explicitly).

Negative arguments of 'fill' are bright green since a few commits.
So now color all valid numeric arguments in that same style -- the
yellow was hard to see on a dark background anyway.

Also, color a zero tabsize as invalid.

This partially adresses https://savannah.gnu.org/bugs/?50998.

Especially: get rid of the "Up: (dir)" link that points nowhere.

Also, add a horizontal line before the final Table of Contents.

They can be given at the prompt, so it's better to accept them on the
command line too.

Also improve some comments.

And rename the function while there anyway.

A recent change (8dffb00f) removed this ability.  This change restores
it, and also allows reading from standard input multiple times -- maybe
not useful, but it works.

Also, conditionalize a statement that is only effective when
multiple file buffers are available.