Move all core types into namespaces (#1886)

* Reorganize namespaces

- Most types are now moved into the `melonDS` namespace
- Only good chance to do this for a while, since a big refactor is next

* Fix the build

src/CRC32.h

@@ -23,6 +23,9 @@
 
 #include "types.h"
 
+namespace melonDS
+{
 u32 CRC32(const u8* data, int len, u32 start=0);
+}
 
 #endif // CRC32_H