Add an unordered_map to TreeEntry for faster lookup

Core/FileSystems/ISOFileSystem.h

@@ -19,6 +19,7 @@
 
 #include <map>
 #include <list>
+#include <unordered_map>
 
 #include "FileSystem.h"
 
@@ -68,7 +69,12 @@ private:
 		bool isDirectory;
 
 		TreeEntry *parent;
-		std::vector<TreeEntry*> children;
+        
+        // slow lookup, in PSP-accurate sorting order
+		std::vector<TreeEntry *> children;
+        
+        // fast lookup, in undefined order
+        std::unordered_map<std::string, TreeEntry *> fastChildren;
 	};
 
 	struct OpenFileEntry