Fixed monitoring related issuse and corrected code

Updated file "NppIO.cpp" to deal with issue #3553

However both existing and updated code looks same, but it is not.
command(IDM_VIEW_MONITORING);
looks equal to

buf->stopMonitoring();
checkMenuItem(IDM_VIEW_MONITORING, false);
_toolBar.setCheck(IDM_VIEW_MONITORING, false);
buf->setUserReadOnly(false);
Updated code works on the current file being processed while existing code command(IDM_VIEW_MONITORING); works with current active buffer. Debugging for reported case can help to understand the above statement.

Justification for updating file "NppCommands.cpp":

See static HANDLE hThread gets a handle when monitoring is activated on a tab.
This handle is overwritten if monitoring is activated on another tab. Resource leak happens here as previous handle can't be closed at all.
However, this handle is not used anywhere in the code, then just why not to close the handle as soon thread is created.

Closes #3554, fixes #3553

PowerEditor/src/NppCommands.cpp

@@ -1937,13 +1937,10 @@ void Notepad_plus::command(int id)
 
 		case IDM_VIEW_MONITORING:
 		{
-			static HANDLE hThread = nullptr;
 			Buffer * curBuf = _pEditView->getCurrentBuffer();
 			if (curBuf->isMonitoringOn())
 			{
 				curBuf->stopMonitoring();
-				::CloseHandle(hThread);
-				hThread = nullptr;
 				checkMenuItem(IDM_VIEW_MONITORING, false);
 				_toolBar.setCheck(IDM_VIEW_MONITORING, false);
 				curBuf->setUserReadOnly(false);
@@ -1963,7 +1960,8 @@ void Notepad_plus::command(int id)
 						curBuf->setUserReadOnly(true);
 						
 						MonitorInfo *monitorInfo = new MonitorInfo(curBuf, _pPublicInterface->getHSelf());
-						hThread = ::CreateThread(NULL, 0, monitorFileOnChange, (void *)monitorInfo, 0, NULL); // will be deallocated while quitting thread
+						HANDLE hThread = ::CreateThread(NULL, 0, monitorFileOnChange, (void *)monitorInfo, 0, NULL); // will be deallocated while quitting thread
+						::CloseHandle(hThread);
 						checkMenuItem(IDM_VIEW_MONITORING, true);
 						_toolBar.setCheck(IDM_VIEW_MONITORING, true);
 					}

PowerEditor/src/NppIO.cpp

@@ -648,7 +648,11 @@ void Notepad_plus::doClose(BufferID id, int whichOne, bool doDeleteBackup)
 	if (buf->isMonitoringOn())
 	{
 		// turn off monitoring
-		command(IDM_VIEW_MONITORING);
+		//command(IDM_VIEW_MONITORING);
+		buf->stopMonitoring();
+		checkMenuItem(IDM_VIEW_MONITORING, false);
+		_toolBar.setCheck(IDM_VIEW_MONITORING, false);
+		buf->setUserReadOnly(false);
 	}
 
 	//Do all the works