[kernel] Have process_start syscall take a list of handles

This also prompted a change of the process initialization protocol to
allow handles to get typed, and changing to marking them as just
self/other handls. This also means exposing the object type enum to
userspace.

src/include/j6/init.h

@@ -3,18 +3,25 @@
 /// Types used in process and thread initialization
 
 #include <stdint.h>
+#include "j6/types.h"
 
 enum j6_init_type {					// `value` is a:
-	j6_init_handle_system,			// Handle to the system
-	j6_init_handle_process,			// Handle to this process
-	j6_init_handle_thread,			// Handle to this thread
-	j6_init_handle_space,			// Handle to this process' address space
+	j6_init_handle_self,			// Handle to the system
+	j6_init_handle_other,			// Handle to this process
 	j6_init_desc_framebuffer		// Pointer to a j6_init_framebuffer descriptor
 };
 
+struct j6_typed_handle {
+	enum j6_object_type type;
+	j6_handle_t handle;
+};
+
 struct j6_init_value {
 	enum j6_init_type type;
-	uint64_t value;
+	union {
+		struct j6_typed_handle handle;
+		void *data;
+	};
 };
 
 /// Structure defining a framebuffer.