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.

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.

Achieve this by making the suppression flag global, so that we can
just reset it instead of making an improper call of do_cursorpos().

This fixes the secondary part of https://savannah.gnu.org/bugs/?51134.

When spotlighting the string to be replaced, placewewant isn't valid,
so tell place_the_cursor() to ignore its value to avoid the cursor
getting mistakenly placed at the beginning of the next row.

This fixes https://savannah.gnu.org/bugs/?50997

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

And in the process transform the token DISABLE_HELP to ENABLE_HELP.

Call something a buffer when it refers to a linked list of linestructs,
and call something a linestruct when it is a struct that describes a
single line.

Also avoid an unused-variable warning, and trim a useless assert.

Because nothing gets reset to zero or to some initial value.

This fixes https://savannah.gnu.org/bugs/?47131.

When the user chooses not to open a file that some message refers to,
remove all messages for that file from the linting results, so the user
does not get asked about that same file again.

This fixes https://savannah.gnu.org/bugs/?47130.

The interval 2013-2017 for the Free Software Foundation is valid
because in those years there were releases with changes by either
Chris or David, and the GNU maintainers guide advises to mention
a new year in all files of a package, not just in the ones that
actually changed, and be done with it for the rest of the year.

When Enter is pressed while the cursor is exactly on the current
indent width, remove the blank characters on that line to avoid
creating a line that consists only of trailing whitespace.

(When Enter is pressed somewhere in the middle of the blanks,
however, the whitespace is preserved.)
Suggested-by: Florian Zeitz <florob@babelmonkeys.de>

Verify at startup that the number is not too small.

Rename some variables in the process, and remove two cluttering asserts.

In do_int_spell_fix(), spell-checking text may change firstcolumn if
the next match is offscreen, and spell-checking text after that will
not change it back.  In order to keep the viewport unchanged, we have
to save and restore not just edittop, but firstcolumn as well.

In do_justify(), justifying text may change firstcolumn if the paragraph
ends offscreen, and unjustifying the text again will not change it back.
In order to keep the viewport unchanged, we have to save and restore not
just edittop, but firstcolumn as well.

Since all lines can be partially scrolled off the screen now
(except for the top line of the edit window, which is forthcoming),
ensure_line_is_visible() is no longer needed.

Most of these variables are freed moments later -- reallocating
them is thus a waste of time.

Now that we pull in the gnulib regex module, we can assume it exists.

The mark only needs to be off when calling replace_marked_buffer(),
because this indirectly calls ingraft_buffer(), which fiddles with
the end points if the mark is on.

This fixes https://savannah.gnu.org/bugs/?50415.

Replace partitioning with calls to extract_buffer() and ingraft_buffer().

In addition to pasting the unjustified text back into the buffer at
current[current_x], ingraft_buffer() also deals with renumbering and
updating totsize, so do_justify() doesn't need to do those anymore
when unjustifying.

With read_file() revamped, it now uses partition_filestruct() indirectly
via ingraft_buffer(), so we can't use partition_filestruct() to replace
marked text in the alternate spell checker anymore without segfaulting.

Add the new function replace_marked_buffer() to accomplish this instead.
Based on replace_buffer(), it uses extract_buffer() to throw away the
marked un-spell-checked text, and then uses read_file() to insert the
spell-checked text at the position where the mark was.

Accordingly, remove unneeded partitioning and related stuff from
do_alt_speller().  Besides pasting the file into the buffer at
current[current_x], ingraft_buffer() also deals with renumbering,
updating totsize, and handling a magicline, so do_alt_speller()
doesn't need to do those anymore.

In this last loop of break_line(), the pointer 'line' is one step ahead
of the index 'lastblank'.  So the loop should first add the length of
the preceding character to 'lastblank' before determining the length
of the current character (and using this to advance 'line').

(There is something wrong in the last loop: line is one character ahead
of lastblank, but the current character length is added to both of them.
It thus assumes that all blank characters are the same number of bytes.
For spaces and tabs this works fine.  But for more exotic blanks...)

Also, remove an assert and adjust some comments.

Also, rename a parameter to be less cryptic, and remove an entire
condition because the relevant block will never be reached when
getting called from the help routines: if blank_loc is negative,
the function will have bailed out in the preceding if.

This fixes https://savannah.gnu.org/bugs/?50379.

The name "filestruct" was a mistake.  What was meant was:
buffer -- a linked list of structs that each describe a line.