[merge] branch 'heapswitch'

This picks up the major work of allowing multiple heap implementations
and enable dlmalloc as an alternate heap to the simple existing one
(now called 'miniheap').

Also added a novm page allocator for memory management on systems too small
or missing an mmu to have a vm. Not much more than a simple bitmap allocator
that the heap pulls from. Allows for other heaps and/or users of physical
memory to coexist and span multiple banks of memory.

app/tests/mem_tests.c

@@ -225,7 +225,7 @@ usage:
         free(ptr);
 #endif
     } else if (argc == 3) {
-        void *ptr = (void *)argv[1].u;
+        void *ptr = argv[1].p;
         size_t len = argv[2].u;
 
         /* run the tests */