[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/libraries/libc/include/stdalign.h

@@ -5,8 +5,10 @@
    Permission is granted to use, modify, and / or redistribute at will.
 */
 
+#ifndef __cplusplus
 #define alignas _Alignas
 #define alignof _Alignof
+#endif
 
 #define __alignas_is_defined 1
 #define __alignof_is_defined 1