[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/kernel.module

@@ -20,6 +20,7 @@ kernel = module("kernel",
         "frame_allocator.cpp",
         "gdt.cpp",
         "gdtidt.s",
+        "heap_allocator.cpp",
         "hpet.cpp",
         "idt.cpp",
         "interrupts.cpp",
@@ -27,6 +28,7 @@ kernel = module("kernel",
         "io.cpp",
         "log.cpp",
         "logger.cpp",
+        "memory.cpp",
         "memory_bootstrap.cpp",
         "msr.cpp",
         "objects/channel.cpp",