AssetManager: Match allocators (#1205)

Currently on line 116 of AssetManager.cpp, we have the following
`*data = (char*)malloc(*len);`
however on line 45 of AssetManager.h we have `delete m_Base;` which is not the same allocator as we used to allocate the memory.
This PR matches the malloc and free to be the correct calls.

dCommon/dClient/AssetManager.h

@@ -42,7 +42,7 @@ struct AssetMemoryBuffer : std::streambuf {
 	}
 
 	void close() {
-		delete m_Base;
+		free(m_Base);
 	}
 };