kernel: separate headers into kernel and user headers

all kernel headers have been moved from include/mango to include/kernel
and include definitions that are only relevant to kernel-space.

any definitions that are relevant to both kernel- and user-space
(i.e. type definitions, syscall IDs) have been moved to
include/mango within libmango.

arch/x86_64/init.c

@@ -2,21 +2,21 @@
 #include <arch/pit.h>
 #include <arch/serial.h>
 #include <arch/vgacon.h>
-#include <mango/arg.h>
-#include <mango/bsp.h>
-#include <mango/clock.h>
-#include <mango/console.h>
-#include <mango/cpu.h>
-#include <mango/init.h>
-#include <mango/libc/stdio.h>
-#include <mango/machine/cpu.h>
-#include <mango/memblock.h>
-#include <mango/object.h>
-#include <mango/percpu.h>
-#include <mango/pmap.h>
-#include <mango/printk.h>
-#include <mango/types.h>
-#include <mango/vm.h>
+#include <kernel/arg.h>
+#include <kernel/bsp.h>
+#include <kernel/clock.h>
+#include <kernel/console.h>
+#include <kernel/cpu.h>
+#include <kernel/init.h>
+#include <kernel/libc/stdio.h>
+#include <kernel/machine/cpu.h>
+#include <kernel/memblock.h>
+#include <kernel/object.h>
+#include <kernel/percpu.h>
+#include <kernel/pmap.h>
+#include <kernel/printk.h>
+#include <kernel/types.h>
+#include <kernel/vm.h>
 
 #define PTR32(x) ((void *)((uintptr_t)(x)))