Kernel: Add kfree_sized(), kfree() with a known allocation size

C++14 gave us sized operator delete, but we haven't been taking
advantage of it. Let's get to a point where it can help us by
adding kfree_sized(void*, size_t).

Kernel/Heap/kmalloc.h

@@ -42,6 +42,7 @@ void kmalloc_init();
 
 void* krealloc(void*, size_t);
 void kfree(void*);
+void kfree_sized(void*, size_t);
 
 struct kmalloc_stats {
     size_t bytes_allocated;