[kernel] Add channel objects

Add the channel object for sending messages between threads. Currently
no good of passing channels to other threads, but global variables in a
single process work. Currently channels are slow and do double copies,
need to refine more.

Tags: ipc

src/kernel/objects/kobject.h

@@ -19,6 +19,7 @@ public:
 
 		event,
 		eventpair,
+		channel,
 
 		vms,
 		vmo,
@@ -55,6 +56,10 @@ public:
 	/// \arg s  The set of signals to deassert
 	void deassert_signal(j6_signal_t s);
 
+	/// Check if the given signals are set on this object
+	/// \arg s  The set of signals to check
+	inline bool check_signal(j6_signal_t s) const { return (m_signals & s) == s; }
+
 	/// Increment the handle refcount
 	inline void handle_retain() { ++m_handle_count; }