Make considerably more progress on AARCH64

- Utilities like pledge.com now build
- kprintf() will no longer balk at 48-bit addresses
- There's a new aarch64-dbg build mode that should work
- gc() and defer() are mostly pacified; avoid using them on aarch64
- THIRD_PART_STB now has Arm Neon intrinsics for fast image handling

tool/net/lfuncs.c

@@ -69,7 +69,11 @@
 #include "third_party/zlib/zlib.h"
 
 static int Rdpid(void) {
+#ifdef __x86_64__
   return rdpid();
+#else
+  return -1;
+#endif
 }
 
 int LuaHex(lua_State *L) {