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.

vm/sparse.c

@@ -22,14 +22,14 @@
    of the sparse memory model may be outweighed by the extra
    overhead, and the flat memory model may be a better choice.
  */
-#include <mango/arg.h>
-#include <mango/bsp.h>
-#include <mango/machine/cpu.h>
-#include <mango/memblock.h>
-#include <mango/panic.h>
-#include <mango/printk.h>
-#include <mango/util.h>
-#include <mango/vm.h>
+#include <kernel/arg.h>
+#include <kernel/bsp.h>
+#include <kernel/machine/cpu.h>
+#include <kernel/memblock.h>
+#include <kernel/panic.h>
+#include <kernel/printk.h>
+#include <kernel/util.h>
+#include <kernel/vm.h>
 
 static struct vm_sector *sector_array = NULL;
 static size_t sector_array_count = 0;