Update kernel makefile, test more kernel code

sw/Makefile

@@ -1,4 +1,4 @@
-.PHONY: all install bios kernel clean
+.PHONY: all install bios kernel clean distclean
 
 all: toolchain bios kernel
 
@@ -15,8 +15,9 @@ bios:
 kernel:
 	@$(MAKE) -C kernel
 
+distclean: clean
+	@$(MAKE) -C cc65  --no-print-directory $@
 
 clean:
 	@$(MAKE) -C bios  --no-print-directory $@
 	@$(MAKE) -C kernel  --no-print-directory $@
-	@$(MAKE) -C cc65  --no-print-directory $@

sw/kernel/kernel.c

@@ -13,8 +13,10 @@
 
 int main() {
     char* string = "this is a shorter string";
-    cputs("Kernel");
-
+    int val = 42;
+    cputs("Kernel\n");
+    cprintf("Kernel printf\n");
+    cprintf("Val: %d\n", val);
     cprintf("%s", string);
 
     // cprintf("Here is a long string: %s\n", longstring);