DiscIO: Make factory methods return unique_ptrs

Rather than rely on the developer to do the right thing,
just make the default behavior safely deallocate resources.

If shared semantics are ever needed in the future, the
constructor that takes a unique_ptr for shared_ptr can
be used.

Source/Core/DiscIO/Blob.h

@@ -14,6 +14,7 @@
 // detect whether the file is a compressed blob, or just a big hunk of data, or a drive, and
 // automatically do the right thing.
 
+#include <memory>
 #include <string>
 #include "Common/CommonTypes.h"
 
@@ -75,7 +76,7 @@ private:
 };
 
 // Factory function - examines the path to choose the right type of IBlobReader, and returns one.
-IBlobReader* CreateBlobReader(const std::string& filename);
+std::unique_ptr<IBlobReader> CreateBlobReader(const std::string& filename);
 
 typedef bool (*CompressCB)(const std::string& text, float percent, void* arg);