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/types.h

@@ -21,6 +21,8 @@
 
 #include <stdint.h>
 
+namespace melonDS
+{
 typedef uint8_t     u8;
 typedef uint16_t    u16;
 typedef uint32_t    u32;
@@ -30,4 +32,5 @@ typedef int16_t     s16;
 typedef int32_t     s32;
 typedef int64_t     s64;
 
+}
 #endif // TYPES_H