core: move new object system to core module

this will allow a wider range of data structures (e.g. b_error, b_stream, b_stringstream) to make use
of the new object system, and other modules and library users can use the object system without
depending on the blue-object or blue-ds modules.

blue-ds will become a simple library of data structures (string, hashmap, etc), built on top of the
core object system.

core/object.h

@@ -0,0 +1,19 @@
+#ifndef _OBJECT_H_
+#define _OBJECT_H_
+
+#include <blue/core/error.h>
+#include <blue/core/misc.h>
+#include <stdint.h>
+
+struct b_type_registration;
+
+struct _b_object {
+	uint64_t obj_magic;
+	const struct b_type_registration *obj_type;
+	unsigned int obj_ref, obj_main_priv_offset;
+};
+
+extern b_result b_object_instantiate(
+	struct b_type_registration *type, struct _b_object **out);
+
+#endif