Hide declaration of gets(3) for C11 and later.

gets(3) was removed from C11.

This reverts commit 1291680c2a0c23b2163198d27e00261ca206298b.

Bug: 14500800
Change-Id: I5e5146bdbb80f2be818a17f287b112bab37d1f6d
diff --git a/libstdc++/include/cstdio b/libstdc++/include/cstdio
index 3c8b5c6..2948d85 100644
--- a/libstdc++/include/cstdio
+++ b/libstdc++/include/cstdio
@@ -63,7 +63,9 @@
 using ::fwrite;
 using ::getc;
 using ::getchar;
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112L
 using ::gets;
+#endif
 using ::perror;
 using ::printf;
 using ::putc;