tweaks: always directly do a refresh when the margin changes

The previous code only directly refreshed the screen when the margin
changed due to toggling line numbering on.  When the margin changed
due to toggling it off, it would indirectly refresh via do_toggle().

src/nano.c

@@ -1383,9 +1383,6 @@ void do_toggle(int flag)
 	    titlebar(NULL);	/* Fall through. */
 #ifndef DISABLE_COLOR
 	case NO_COLOR_SYNTAX:
-#endif
-#ifdef ENABLE_LINENUMBERS
-	case LINE_NUMBERS:
 #endif
 	case SOFTWRAP:
 	    refresh_needed = TRUE;
@@ -2646,19 +2643,16 @@ int main(int argc, char **argv)
 	int needed_margin = digits(openfile->filebot->lineno) + 1;
 
 	/* Only enable line numbers when there is enough room for them. */
-	if (ISSET(LINE_NUMBERS) && needed_margin < COLS - 3) {
-	    if (needed_margin != margin) {
-		margin = needed_margin;
-		editwincols = COLS - margin;
-		/* The margin has changed -- schedule a full refresh. */
-		refresh_needed = TRUE;
-	    }
-	} else
-#endif
-	{
-	    margin = 0;
-	    editwincols = COLS;
+	if (!ISSET(LINE_NUMBERS) || needed_margin > COLS - 4)
+	    needed_margin = 0;
+
+	if (needed_margin != margin) {
+	    margin = needed_margin;
+	    editwincols = COLS - margin;
+	    /* The margin has changed -- schedule a full refresh. */
+	    refresh_needed = TRUE;
 	}
+#endif
 
 	if (currmenu != MMAIN)
 	    display_main_list();