user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/sysdeps/vinix/generic/syscall.h

@@ -0,0 +1,16 @@
+#include <stdint.h>
+
+struct __syscall_ret {
+	uint64_t ret;
+	uint64_t errno;
+};
+
+__attribute__((naked))
+static __syscall_ret __syscall(int number, ...) {
+	asm (
+		"mov %rcx, %r10\n\t"
+		"syscall\n\t"
+		"ret"
+	);
+	(void)number;
+}