user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/tests/ansi/locale.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <wchar.h>
+#include <limits.h>
+#include <locale.h>
+#include <assert.h>
+
+int main() {
+	wchar_t c = 0xC9;
+	unsigned char buf[MB_LEN_MAX] = { 0 };
+	setlocale(LC_ALL, "");
+	if (sprintf(buf, "%lc", c) < 0)
+		return -1;
+
+	assert(buf[0] == 0xc3 && buf[1] == 0x89
+			&& buf[2] == '\0' && buf[3] == '\0');
+
+	return 0;
+}