[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/memory.cpp

@@ -0,0 +1,37 @@
+#include "memory.h"
+
+namespace std {
+    enum class __attribute__ ((__type_visibility("default"))) align_val_t : size_t { };
+}
+
+// Implementation of memset and memcpy because we're not
+// linking libc into the kernel
+extern "C" {
+
+void *
+memset(void *s, uint8_t v, size_t n)
+{
+    uint8_t *p = reinterpret_cast<uint8_t *>(s);
+    for (size_t i = 0; i < n; ++i) p[i] = v;
+    return s;
+}
+
+void *
+memcpy(void *dest, const void *src, size_t n)
+{
+    const uint8_t *s = reinterpret_cast<const uint8_t *>(src);
+    uint8_t *d = reinterpret_cast<uint8_t *>(dest);
+    for (size_t i = 0; i < n; ++i) d[i] = s[i];
+    return d;
+}
+
+}
+
+uint8_t
+checksum(const void *p, size_t len, size_t off)
+{
+    uint8_t sum = 0;
+    const uint8_t *c = reinterpret_cast<const uint8_t *>(p);
+    for (int i = off; i < len; ++i) sum += c[i];
+    return sum;
+}