filesystem restructure work.

Add mount/unmountCommonPath, mount/unmountFullPath, getFullCommonPath.

Reimplement identity and save directory code in terms of new commonpath code.

Add internal createRealDirectory function (not exposed, currently).

src/common/apple.h

@@ -38,10 +38,10 @@ enum UserDirectory
 	USER_DIRECTORY_DOCUMENTS,
 	USER_DIRECTORY_DESKTOP,
 	USER_DIRECTORY_CACHES,
+	USER_DIRECTORY_TEMP,
 };
 
 std::string getUserDirectory(UserDirectory dir);
-
 std::string getExecutablePath();
 
 } // apple