menuconfig: Add Save/Load buttons

If menuconfig have Save/Load button like alternative
.config editors, xconfig, nconfig, etc.We will have
a obvious benefit when use menuconfig just like
when we use others, we can Save/Load our .config quickly
and conveniently.

This patch add the Save/Load button for menuconfig.

[remove trailing space while at it for below line:
"*)  Formerly when I used Page Down and Page Up, the cursor would be set"
]

Changes:
V1-V2:
1:use PATH_MAX instead of hard code suggested by Yann E. MORIN
2:drop the spurious empty-line removal suggested by Yann E. MORIN
V2-V3:
1:ajust buttons position well centered reported by Yann E. MORIN

Signed-off-by: Wang YanQing <udknight@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
diff --git a/scripts/kconfig/lxdialog/menubox.c b/scripts/kconfig/lxdialog/menubox.c
index 1d60473..48d382e 100644
--- a/scripts/kconfig/lxdialog/menubox.c
+++ b/scripts/kconfig/lxdialog/menubox.c
@@ -26,7 +26,7 @@
  *
  *    *)  A bugfix for the Page-Down problem
  *
- *    *)  Formerly when I used Page Down and Page Up, the cursor would be set 
+ *    *)  Formerly when I used Page Down and Page Up, the cursor would be set
  *        to the first position in the menu box.  Now lxdialog is a bit
  *        smarter and works more like other menu systems (just have a look at
  *        it).
@@ -154,12 +154,14 @@
  */
 static void print_buttons(WINDOW * win, int height, int width, int selected)
 {
-	int x = width / 2 - 16;
+	int x = width / 2 - 28;
 	int y = height - 2;
 
 	print_button(win, gettext("Select"), y, x, selected == 0);
 	print_button(win, gettext(" Exit "), y, x + 12, selected == 1);
 	print_button(win, gettext(" Help "), y, x + 24, selected == 2);
+	print_button(win, gettext(" Save "), y, x + 36, selected == 3);
+	print_button(win, gettext(" Load "), y, x + 48, selected == 4);
 
 	wmove(win, y, x + 1 + 12 * selected);
 	wrefresh(win);
@@ -372,7 +374,7 @@
 		case TAB:
 		case KEY_RIGHT:
 			button = ((key == KEY_LEFT ? --button : ++button) < 0)
-			    ? 2 : (button > 2 ? 0 : button);
+			    ? 4 : (button > 4 ? 0 : button);
 
 			print_buttons(dialog, height, width, button);
 			wrefresh(menu);
@@ -399,17 +401,17 @@
 				return 2;
 			case 's':
 			case 'y':
-				return 3;
-			case 'n':
-				return 4;
-			case 'm':
 				return 5;
-			case ' ':
+			case 'n':
 				return 6;
-			case '/':
+			case 'm':
 				return 7;
-			case 'z':
+			case ' ':
 				return 8;
+			case '/':
+				return 9;
+			case 'z':
+				return 10;
 			case '\n':
 				return button;
 			}