user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/rtld/rtld_next/test.c

@@ -0,0 +1,28 @@
+#include <string.h>
+#include <assert.h>
+
+typedef char *charFn(void);
+charFn *fooGetDefault(void);
+charFn *fooGetNext(void);
+charFn *barGetDefault(void);
+charFn *barGetNext(void);
+
+int main() {
+	charFn *ret;
+
+	ret = fooGetDefault();
+	assert(ret != NULL);
+	assert(!strcmp(ret(), "foo"));
+
+	ret = fooGetNext();
+	assert(ret != NULL);
+	assert(!strcmp(ret(), "bar"));
+
+	ret = barGetDefault();
+	assert(ret != NULL);
+	assert(!strcmp(ret(), "foo"));
+
+	assert(barGetNext() == NULL);
+
+	return 0;
+}