user: implement mlibc as the libc, finally.

It's finally done..

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

ext2_root/usr/include/bits/ssize_t.h

@@ -0,0 +1,15 @@
+
+#ifndef MLIBC_SSIZE_T_H
+#define MLIBC_SSIZE_T_H
+
+/* TODO: use ptrdiff_t instead? */
+#if __UINTPTR_MAX__ == __UINT64_MAX__
+typedef long ssize_t;
+#elif __UINTPTR_MAX__ == __UINT32_MAX__
+typedef int ssize_t;
+#else
+#error "unsupported architecture"
+#endif
+
+#endif /* MLIBC_SSIZE_T_H */
+