Fix issue WinMerge#2635: /inifile won't work with root directory

Src/paths.cpp

@@ -161,7 +161,7 @@ static bool IsDirName(const String& sDir)
 	// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/fs/findfirstfile.asp
 	// You cannot use root directories as the lpFileName input string for FindFirstFile - with or without a trailing backslash.
 	size_t count = 0;
-	if ((sDir[0] && sDir[1] == ':' && sDir[2] == '\0') ||
+	if ((sDir[0] && sDir[1] == ':' && (sDir[2] == '\0' || (sDir[2] == '\\' && sDir[3] == '\0'))) ||
 	    // \\host\share or \\host\share\ 
 	    (sDir[0] == '\\' && sDir[1] == '\\' && 
 	     (count = std::count(sDir.begin(), sDir.end(), ('\\'))) <= 4 &&