user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/tests/rtld/preinit/libfoo.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <assert.h>
+
+int fooDone = 0;
+
+// DSOs do not support pre-initialization functions.
+
+__attribute__((constructor))
+void fooInit() {
+	dprintf(1, "initialization function called in foo\n");
+
+	assert(fooDone == 0);
+	fooDone++;
+}
+
+int isFooDone() {
+	return fooDone;
+}