fixes for A2

mostly include some things that should and remove some things that shouldn't have been included in the handout (yes this does hint at some places that need to be touched for A2)

kernel/memory/pagefault.cc

@@ -29,7 +29,7 @@ assert_size(ErrorCode, 4);
 												 uint64_t err) {
 	PageFault::ErrorCode error(err);
 	// Get the faulting address
-	uintptr_t virt;
+	uintptr_t virt = 0;
 	asm volatile("mov %%cr2, %0" : "=r"(virt));
 	DBG << "Page fault at " << hex << virt << dec << endl;