MdeModulePkg/BMUiLib: Check reset requirement before exiting UiApp

V2: Refine the comments.

In UI page, some configuration change may require system reset.
BootManagerUiLib misses this check before exiting UiApp to boot
other boot options. Now add the check.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdeModulePkg/Library/BootManagerUiLib/BootManager.h

@@ -1,7 +1,7 @@
 /** @file
   The boot manager reference implementation
 
-Copyright (c) 2004 - 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2004 - 2017, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials are licensed and made available under
 the terms and conditions of the BSD License that accompanies this distribution.
 The full text of the license may be found at
@@ -20,6 +20,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 #include <Protocol/HiiConfigAccess.h>
 #include <Protocol/DevicePathToText.h>
+#include <Protocol/FormBrowserEx2.h>
 
 #include <Library/PrintLib.h>
 #include <Library/DebugLib.h>
@@ -55,6 +56,7 @@ typedef struct {
 
 #define LABEL_BOOT_OPTION        0x00
 #define LABEL_BOOT_OPTION_END    0x01
+#define MAX_STRING_LEN           200
 
 //
 // Variable created with this flag will be "Efi:...."