docs: document the effect of --quickblank together with --zero/--minibar

doc/nano.1

@@ -192,8 +192,11 @@ Set the size (width) of a tab to \fInumber\fP columns.  The value of
 .TP
 .BR \-U ", " \-\-quickblank
 Make status-bar messages disappear after 1 keystroke instead of after 20.
-Note that options \fB\-c\fR (\fB\-\-constantshow\fR)
+Note that option \fB\-c\fR (\fB\-\-constantshow\fR) overrides this.
-and \fB\-_\fR (\fB\-\-minibar\fR) override this.
+When option \fB\-\-minibar\fR or \fB\-\-zero\fR is in effect,
+\fB\-\-quickblank\fR makes a message disappear after
+0.8 seconds instead of after the default 1.5 seconds.
+.
 .TP
 .BR \-V ", " \-\-version
 Show the current version number and exit.

doc/nano.texi

@@ -487,8 +487,10 @@ Set the displayed tab length to @var{number} columns.  The value of
 @item -U
 @itemx --quickblank
 Make status-bar messages disappear after 1 keystroke instead of after 20.
-Note that options @option{-c} (@option{--constantshow})
+Note that option @option{-c} (@option{--constantshow}) overrides this.
-and @option{-_} (@option{--minibar}) override this.
+When option @option{--minibar} or @option{--zero} is in effect,
+@option{--quickblank} makes a message disappear after
+0.8 seconds instead of after the default 1.5 seconds.
 
 @item -V
 @itemx --version
@@ -1034,7 +1036,10 @@ The default value is "@t{!.?}".
 
 @item set quickblank
 Make status-bar messages disappear after 1 keystroke instead of after 20.
-Note that options @option{constantshow} and @option{minibar} override this.
+Note that option @option{constantshow} overrides this.
+When option @option{minibar} or @option{zero} is in effect,
+@option{quickblank} makes a message disappear after
+0.8 seconds instead of after the default 1.5 seconds.
 
 @item set quotestr "@var{regex}"
 Set the regular expression for matching the quoting part of a line.

doc/nanorc.5

@@ -258,7 +258,10 @@ specfified closing punctuation, optionally followed by closing brackets
 .TP
 .B set quickblank
 Make status-bar messages disappear after 1 keystroke instead of after 20.
-Note that options \fBconstantshow\fR and \fBminibar\fR override this.
+Note that option \fBconstantshow\fR overrides this.
+When option \fBminibar\fR or \fBzero\fR is in effect,
+\fBquickblank\fR makes a message disappear after
+0.8 seconds instead of after the default 1.5 seconds.
 .TP
 .BI "set quotestr """ regex """
 Set the regular expression for matching the quoting part of a line.