add support for Arm MTE memory tagging

- tag slab allocations with [1..14] tags
- tag freed slab allocations with the "15" tag value to detect accesses to freed slab memory
- when generating tag value for a slab slot, always exclude most recent tag value for that slot
(to make use-after-free detection more reliable) and most recent tag values of its immediate
neighbors (to detect linear overflows and underflows)

memory.h

@@ -11,6 +11,9 @@
 int get_metadata_key(void);
 
 void *memory_map(size_t size);
+#ifdef HAS_ARM_MTE
+void *memory_map_mte(size_t size);
+#endif
 bool memory_map_fixed(void *ptr, size_t size);
 bool memory_unmap(void *ptr, size_t size);
 bool memory_protect_ro(void *ptr, size_t size);