toolchain: add new debugging tool using magenta_debug

toolchain/mxdbg/client/memory.c

@@ -0,0 +1,19 @@
+#include "command.h"
+
+#include <stdio.h>
+
+static int memory(
+	const struct command *cmd,
+	struct debug_context *ctx,
+	int argc,
+	const char **argv,
+	void *argp)
+{
+	printf("inspect memory\n");
+	return 0;
+}
+
+const struct command cmd_memory = {
+	.cmd_name = "memory",
+	.cmd_callback = memory,
+};