When the user wants to get a backtrace, the crash handler shouldn't
kick in.

Upon a segmentation fault or an abort signal, instead of crashing,
losing all changes, and leaving the terminal in curses mode, nano
now calls die(), to save any changed buffers and to restore the
terminal to a usable state.

For the remote chance that nano segfaults in die(), the handler for
SIGSEGV and for SIGABRT is reset to its default value as soon as the
signal fires, to prevent a crash-handler loop.

Since a core dump is usually more helpful for debugging, the crash
handler is not included in a debug build.

This addresses https://savannah.gnu.org/patch/?9623

.
Signed-off-by: Devin Hussey <husseydevin@gmail.com>

Also, add a period after the "Read nn lines" message, and
don't let the next shell prompt overwrite this message.

This addresses https://savannah.gnu.org/bugs/?53779.

Also remove two notes that are obsolete by now.

This addresses https://savannah.gnu.org/bugs/?53777.

This makes the names of these bindable functions equal to the names of
their corresponding options -- like for all the other toggles that have
a corresponding option.

This makes the line-numbers toggle rebindable, like all the others.

Set the NO_NEWLINES flag to achieve this.  And move the saving and
restoring of the global flags to the main speller routine, so the
flags aren't saved and restored for each internal spell fix.

This fixes https://savannah.gnu.org/bugs/?53742

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

There is no longer any need to burden the translators with also
providing the English letters.

This fixes https://savannah.gnu.org/bugs/?53735.

When the cursor is on the top or bottom line of the edit window, and
an <Up> or <Down> pushes the cursor offscreen, then use edit_scroll()
to bring it back into view, instead of using edit_redraw(), because
the latter would redraw *every row* on the screen, which is a waste
of time.

This addresses https://savannah.gnu.org/bugs/?53562

.
Reported-by: Devin Hussey <husseydevin@gmail.com>

This fixes https://savannah.gnu.org/bugs/?53723.

Bug existed since commit 30fc197b (a month ago) which changed the
type of 'i' from int to size_t, causing the comparison to do the
wrong thing when 'threshold' is negative.

This fixes https://savannah.gnu.org/bugs/?53722

.
Reported-by: Devin Hussey <husseydevin@gmail.com>

Don't try to re-enter curses mode when the terminal is not in
the correct state yet.

This fixes https://savannah.gnu.org/bugs/?53720.

The formatter or linter might have changed in the meantime -- when
the filename was changed to have a different extension, for example.

This fixes https://savannah.gnu.org/bugs/?53716.

When the user configures nano with --enable-altrcname=name,
the specified name should not be prefixed with a dot.

This fixes https://savannah.gnu.org/bugs/?53694

.
Reported-by: Cody A. Taylor <codemister99@yahoo.com>

Especially color \a and \t, to make it easier to distinguish them
from contiguous text.

When the keyboard buffer is empty, return a value that is not equivalent
to <Ctrl+Space>, so that typing a bunch of these while searching is going
on will not result in some of them getting executed afterward.

It is not an abort but simply a bit of cleaning up.

Also adjust and correct a comment.

This makes it easier to predict in which direction the replacements
will go when hitting ^\ or M-R.
Signed-off-by: Liu Hao <lh_mouse@126.com>