statusbar: leave out the brackets when the message is very long

This also prevents the message from spilling into the help lines
when the terminal is less than four columns wide.  (Not that one
can read anything then, but it looks better.)

src/winio.c

@@ -1958,6 +1958,7 @@ void statusline(message_type importance, const char *msg, ...)
     va_list ap;
     char *bar, *foo;
     size_t start_x;
+    bool bracketed;
 #ifndef NANO_TINY
     bool old_whitespace = ISSET(WHITESPACE_DISPLAY);
 
@@ -1993,24 +1994,27 @@ void statusline(message_type importance, const char *msg, ...)
 
     blank_statusbar();
 
-    bar = charalloc(mb_cur_max() * (COLS - 3));
-    vsnprintf(bar, mb_cur_max() * (COLS - 3), msg, ap);
+    bar = charalloc(mb_cur_max() * (COLS + 1));
+    vsnprintf(bar, mb_cur_max() * (COLS + 1), msg, ap);
     va_end(ap);
-    foo = display_string(bar, 0, COLS - 4, FALSE);
+    foo = display_string(bar, 0, COLS, FALSE);
     free(bar);
 
 #ifndef NANO_TINY
     if (old_whitespace)
 	SET(WHITESPACE_DISPLAY);
 #endif
-    start_x = (COLS - strlenpt(foo) - 4) / 2;
+    start_x = (COLS - strlenpt(foo)) / 2;
+    bracketed = (start_x > 1);
 
-    wmove(bottomwin, 0, start_x);
+    wmove(bottomwin, 0, (bracketed ? start_x - 2 : start_x));
     wattron(bottomwin, interface_color_pair[STATUS_BAR]);
-    waddstr(bottomwin, "[ ");
+    if (bracketed)
+	waddstr(bottomwin, "[ ");
     waddstr(bottomwin, foo);
     free(foo);
-    waddstr(bottomwin, " ]");
+    if (bracketed)
+	waddstr(bottomwin, " ]");
     wattroff(bottomwin, interface_color_pair[STATUS_BAR]);
 
     /* Push the message to the screen straightaway. */