Command to print total kernel heap usage for debugging.

kern/include/lib.h

@@ -129,6 +129,7 @@ uint32_t random(void);
 void *kmalloc(size_t size);
 void kfree(void *ptr);
 void kheap_printstats(void);
+void kheap_printused(void);
 void kheap_nextgeneration(void);
 void kheap_dump(void);
 void kheap_dumpall(void);