Fix inconsistencies at OS-forced Notepad++ (v8.4.7) exit

Now if the Notepad++ will have an unsaved data and is still running at the OS restart/shutdown, there will be one universal messagebox "Windows session is about to be terminated but you have some data unsaved. Do you want to exit Notepad++ now?".

When Notepad++ backup mode is ON, answer:
  - YES ... Notepad++ simply quits (Notepad++ backup engine silently handles all the stuff needed)
  - NO  ... Notepad++ stays running, user is on his/her own

When Notepad++ backup mode is OFF, answer:
  - YES ... Notepad++ behaves identically as in the case of the usual Notepad++ IDM_FILE_EXIT or WM_CLOSE messages (save dlgs appears etc., it depends on the current user Notepad++ settings)
  - NO  ... Notepad++ stays running, user is on his/her own

Fix v847

PowerEditor/installer/nativeLang/english.xml

@@ -1377,6 +1377,7 @@ Notepad++ will be restarted after all the operations are terminated.
 Continue?"/>
             <NeedToRestartToLoadPlugins title="Notepad++ need to be relaunched" message="You have to restart Notepad++ to load plugins you installed."/> <!-- HowToReproduce: Import a plugin via menu "Settings->Import->Import Plugin(s)...". -->
             <ChangeHistoryEnabledWarning title="Notepad++ need to be relaunched" message="You have to restart Notepad++ to enable Change History."/> <!-- HowToReproduce: uncheck "Display Change History" via Preferences dialog "Marges/Border/Edge. -->
+            <WindowsSessionExit title="Notepad++ - Windows session exit" message="Windows session is about to be terminated but you have some data unsaved. Do you want to exit Notepad++ now?"/>
         </MessageBox>
         <ClipboardHistory>
             <PanelTitle name="Clipboard History"/>

PowerEditor/src/NppBigSwitch.cpp

@@ -2106,6 +2106,18 @@ LRESULT Notepad_plus::process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 			return TRUE;
 		}
 
+		case NPPM_INTERNAL_WINDOWSSESSIONEXIT:
+		{
+			int answer = _nativeLangSpeaker.messageBox("WindowsSessionExit",
+				_pPublicInterface->getHSelf(),
+				TEXT("Windows session is about to be terminated but you have some data unsaved. Do you want to exit Notepad++ now?"),
+				TEXT("Notepad++ - Windows session exit"),
+				MB_YESNO | MB_ICONQUESTION | MB_APPLMODAL);
+			if (answer == IDYES)
+				::PostMessage(_pPublicInterface->getHSelf(), WM_CLOSE, 0, 0);
+			return TRUE;
+		}
+
 		case WM_QUERYENDSESSION:
 		{
 			// app should return TRUE or FALSE immediately upon receiving this message,
@@ -2176,7 +2188,7 @@ LRESULT Notepad_plus::process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 								::SendMessage(hwnd, WM_SIZE, 0, 0);	// to make window fit (specially to show tool bar.)
 							}
 						}
-						::PostMessage(hwnd, WM_COMMAND, IDM_FILE_SAVEALL, 0); // posting will not block us here
+						::PostMessage(hwnd, NPPM_INTERNAL_WINDOWSSESSIONEXIT, 0, 0); // posting will not block us here
 						return FALSE; // request abort of the shutdown 
 					}
 				}

PowerEditor/src/resource.h

@@ -643,6 +643,7 @@
 	#define NPPM_INTERNAL_ENABLECHANGEHISTORY           (NOTEPADPLUS_USER_INTERNAL + 67)
 	#define NPPM_INTERNAL_CLEANSMARTHILITING            (NOTEPADPLUS_USER_INTERNAL + 68)
 	#define NPPM_INTERNAL_CLEANBRACEMATCH               (NOTEPADPLUS_USER_INTERNAL + 69)
+	#define NPPM_INTERNAL_WINDOWSSESSIONEXIT            (NOTEPADPLUS_USER_INTERNAL + 70)
 
 // See Notepad_plus_msgs.h
 //#define NOTEPADPLUS_USER   (WM_USER + 1000)