[IO] rework dprintf to take a debug level, defined in DEBUGLEVEL

printf at the moment just calls dprintf, but soon will become
a seperate I/O queue.
diff --git a/kernel/main.c b/kernel/main.c
index cfe39b2..7fa8d59 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -67,30 +67,30 @@
 	// do any super early target initialization
 	target_early_init();
 
-	dprintf("welcome to lk\n\n");
+	dprintf(INFO, "welcome to lk\n\n");
 	
 	// deal with any static constructors
-	dprintf("calling constructors\n");
+	dprintf(SPEW, "calling constructors\n");
 	call_constructors();
 
 	// bring up the kernel heap
-	dprintf("initializing heap\n");
+	dprintf(SPEW, "initializing heap\n");
 	heap_init();
 
 	// initialize the threading system
-	dprintf("initializing threads\n");
+	dprintf(SPEW, "initializing threads\n");
 	thread_init();
 
 	// initialize the dpc system
-	dprintf("initializing dpc\n");
+	dprintf(SPEW, "initializing dpc\n");
 	dpc_init();
 
 	// initialize kernel timers
-	dprintf("initializing timers\n");
+	dprintf(SPEW, "initializing timers\n");
 	timer_init();
 
 	// create a thread to complete system initialization
-	dprintf("creating bootstrap completion thread\n");
+	dprintf(SPEW, "creating bootstrap completion thread\n");
 	thread_resume(thread_create("bootstrap2", &bootstrap2, NULL, DEFAULT_PRIORITY, DEFAULT_STACK_SIZE));
 
 	// enable interrupts
@@ -104,19 +104,19 @@
 
 static int bootstrap2(void *arg)
 {
-	dprintf("top of bootstrap2()\n");
+	dprintf(SPEW, "top of bootstrap2()\n");
 
 	arch_init();
 
 	// initialize the rest of the platform
-	dprintf("initializing rest of platform\n");
+	dprintf(SPEW, "initializing platform\n");
 	platform_init();
-
-	// initialize the rest of the target
-	dprintf("initializing rest of target\n");
+	
+	// initialize the target
+	dprintf(SPEW, "initializing target\n");
 	target_init();
 
-	dprintf("calling project_init()\n");
+	dprintf(SPEW, "calling sys_init()\n");
 	project_init();
 
 	return 0;