Allow heap_manager to use non-contiguous blocks.

* Heap manager can now manage non-contiguous blocks of memory (currently
  all sized at the max block size only)
* Fix a bug where heap manager would try to buddy-merge max-sized blocks

src/libraries/kutil/heap_manager.cpp

@@ -104,7 +104,7 @@ heap_manager::free(void *p)
 	header -= 1; // p points after the header
 	header->set_used(false);
 
-	while (true) {
+	while (header->size() != max_size) {
 		mem_header *buddy = header->buddy();
 		if (buddy->used() || buddy->size() != header->size()) break;
 		buddy->remove();
@@ -124,9 +124,8 @@ heap_manager::grow_memory()
 {
 	size_t length = (1 << max_size);
 
-	void *next = kutil::offset_pointer(m_start, m_length);
 	kassert(m_grow, "Tried to grow heap without a growth callback");
-	m_grow(next, length);
+	void *next = m_grow(kutil::offset_pointer(m_start, m_length), length);
 
 	mem_header *block = new (next) mem_header(nullptr, get_free(max_size), max_size);
 	get_free(max_size) = block;

src/libraries/kutil/include/kutil/heap_manager.h

@@ -11,7 +11,10 @@ namespace kutil {
 class heap_manager
 {
 public:
-	using grow_callback = void (*)(void *start, size_t length);
+	/// Callback signature for growth function. The next pointer is just a
+	/// hint; memory returned does not need to be contiguous, but needs to be
+	/// alined to the length requested.
+	using grow_callback = void * (*)(void *next, size_t length);
 
 	/// Default constructor. Creates an invalid manager.
 	heap_manager();