Fix bug of monitoring not working for files under root

Closes #2061
To reproduce such bug, the file foo.txt to monitor should be in the root folder (ie. c:\foo.txt).
The algorithm is check if folder path has '\' at the end, if no, then add a '\' then append file name.
In the original code, instead of checking folder path, the file name is checked. Since file name doesn't contain '\' (ie. c:\temp), a '\' is always added on folder path which has no '\' at the end. it works for none root folder such as C:\, E:\ or F:\.

PowerEditor/src/WinControls/ReadDirectoryChanges/ReadDirectoryChangesPrivate.cpp

@@ -149,7 +149,7 @@ void CReadChangesRequest::ProcessNotification()
 
 		CStringW wstrFilename(fni.FileName, fni.FileNameLength/sizeof(wchar_t));
 		// Handle a trailing backslash, such as for a root directory.
-		if (wstrFilename.Right(1) != L"\\")
+		if (m_wstrDirectory.Right(1) != L"\\")
 			wstrFilename = m_wstrDirectory + L"\\" + wstrFilename;
 		else
 			wstrFilename = m_wstrDirectory + wstrFilename;