When unindenting/uncommenting affected the bottom line of the marked
region, keep affecting this line also during subsequent consecutive
indenting/commenting.

This fixes https://savannah.gnu.org/bugs/?52718.

So that Commenting comes closer to the somewhat related Indenting
and Unindenting functions.

Also, make the descriptions for indenting/unindenting more precise.

So they will be found quicker.

Also fold two assignments into one.

They were mistakenly added by changeset fb85c055, four commits ago.

This fixes https://savannah.gnu.org/bugs/?52717.

Suggested-by: Brand Huntsman <alpha@qzx.com>

If the marked region ends at the start of a line, do not include that
line in the indenting/undenting or commenting/uncommenting.  This is
closer to what the eye would expect.

Unset the "Modified" marker only at the point where the file was last
saved -- if there is such a point, because it can be missing when the
undo stack was discarded.

This fixes https://savannah.gnu.org/bugs/?52689

.
Reported-by: Liu Hao <lh_mouse@126.com>
Original-idea-by: Brand Huntsman <alpha@qzx.com>

When doing that, there is no need to save and restore the Modified
state when writing a marked region.

This fixes https://savannah.gnu.org/bugs/?52651

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

The escape sequence "Esc [ Z" is a backtab on most supported terminals,
so make sure convert_sequence() treats it as such.

The function get_keycode() should never return zero -- it should
return either the code from ncurses or the given fallback code.

This fixes https://savannah.gnu.org/bugs/?52682.

To achieve that, fake the Shift key being held when indenting/
unindenting/commenting/uncommenting.
Reported-by: Brand Huntsman <alpha@qzx.com>

When the mark is on, instead of letting a <Tab> simply insert a Tab
character at the cursor position, let it indent the marked region.
Original-idea-by: Chris Allegretta <chrisa@asty.org>

Make both preceding character moves include the terminating byte.

The character move has already copied the terminating byte.
And a reallocation to save just one character of memory is
a waste of time.

And also allow it when lines are only partially indented.

This makes it possible to equalize the indentations of (accidentally)
unevenly indented lines: by first fully unindenting a group of lines,
and then reindenting them to the desired amount.
Suggested-by: Liu Hao <lh_mouse@126.com>

In this way we can delete things on the current line with ^K (after
Shift-selecting some text) without nano misdetecting a line change,

This fully fixes https://savannah.gnu.org/bugs/?52576.

Only when the cursor has moved off of the currrent line do we stop
prepending wrapped words to the next line.

This partially fixes https://savannah.gnu.org/bugs/?52576.

The option now causes nano to trim trailing whitespace also when
hardwrapping occurs while the user is typing.

This fulfills https://savannah.gnu.org/bugs/?52198.

To get rid of two double negatives.