Move the initialization of the operating directory to after the
initialization of the screen, so that the above error can be shown.

This fixes the first part of https://savannah.gnu.org/bugs/?47798.

Between the first stat (that sets 'realexists') and the second stat
(directly after), the file might have disappeared, which would mean
that current_stat would be NULL.  Prevent dereferencing this further
down.

Only when the user decides not to override an existing lockfile should
loading the corresponding file be skipped.  Any failure to write the
lockfile should be ignored -- the file itself should be loaded anyway.

This fixes https://savannah.gnu.org/bugs/?47945.

Error messages about lock files should not get overwritten by purely
informational messages, only by alerting ones.

This fixes https://savannah.gnu.org/bugs/?47963.

The variable 'namecopy' has been passed to dirname(), so it is likely
to have been changed when it contains a slash.  So, use a new variable
instead.  Also, free the result of display_string().

This fixes https://savannah.gnu.org/bugs/?47956.

Having just opened a fresh buffer, 'openfile->next' will never be NULL,
because the list is circular.

Second, when compiled with --disable-nultibuffer, and deciding not to
override an existing lock, the 'return FALSE' should *not* be skipped,
because otherwise the named file will be opened after all.

This fixes an unreported bug.

Make the failures to read or write a lock file into important messages,
so they will not be overwritten by the number of lines read.

The general mechanism for not allowing important messages to be overwritten
will take care of not overwriting warnings about failed file lockings.

This fixes https://savannah.gnu.org/bugs/?47954.

Either the selected file was changed, or a file or directory was chosen
(and the Enter key virtually pressed), or a shortcut was executed.  So,
just go and read the next key.

This fixes https://savannah.gnu.org/bugs/?47944.

If during startup there are multiple error messages, currently only the
last one remains and can be read.  To improve on that, introduce a short
pause between error messages -- even if it's not enough to read them all,
at least the user will be aware that there are multiple ones.

This also causes a few error messages to beep that currently don't beep,
such as when a file is unwritable.

When doing a PageUp or PageDown in the browser, don't move the highlight
to the first line in the same column, but keep it in the same relative
position of the screen.  If we're already on the first or last page,
move the highlight to the first or last line, but keep it in the same
column.  If we're already on the first or last line, only then move it
to the first or last entry.

To separate things that have little to do with each other.

When compiled with --disable-justify, try to keep the vertical pairing
of related items.

This fixes https://savannah.gnu.org/bugs/?47933.

This fixes https://savannah.gnu.org/bugs/?47932.

CONST_UPDATE is only relevant when in the main menu, not when in the
browser.  So, check for that condition, instead of saving, changing,
and then restoring the setting.

CONST_UPDATE does not need to influence the delay for blanking the
statusbar; it is enough when it simply prevents it.

When in the browser, typing keys that produce an unknown escape sequence
should not switch on the cursor.

Take the side effect of a 'statusbar' call -- setting suppress_cursorpos
to TRUE -- into account.  This effect was overlooked by commit 9d6d5b67.

The function 'bottombars' has already done this.

An interactive 'gotolinecolumn' has already refreshed the screen.

There is no need to iterate through all the file names, as we already
know the length of the longest.  From this it's easy to calculate how
many names fit on a line.