[kernel] Move more from kutil to kernel

The moving of kernel-only code out of kutil continues. (See 042f061)
This commit moves the following:

- The heap allocator code
- memory.cpp/h which means:
  - letting string.h be the right header for memset and memcpy, still
    including an implementation of it for the kernel though, since
    we're not linking libc to the kernel
  - Changing calls to kalloc/kfree to new/delete in kutil containers
    that aren't going to be merged into the kernel
- Fixing a problem with stdalign.h from libc, which was causing issues
  for type_traits.

src/kernel/syscall.cpp.cog

@@ -1,7 +1,7 @@
 // vim: ft=cpp
 #include <stddef.h>
+#include <string.h>
 
-#include "kutil/memory.h"
 
 #include "console.h"
 #include "debug.h"
@@ -38,7 +38,7 @@ syscall_invalid(uint64_t call)
 void
 syscall_initialize()
 {
-    kutil::memset(&syscall_registry, 0, sizeof(syscall_registry));
+    memset(&syscall_registry, 0, sizeof(syscall_registry));
 
     /*[[[cog code generation
     for id, scope, method in syscalls.methods: