Implement national body comment GB9: remove std::gets

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@192538 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/cstdio b/include/cstdio
index 3bc9659..ce3af4d 100644
--- a/include/cstdio
+++ b/include/cstdio
@@ -74,7 +74,7 @@
 int fputs(const char* restrict s, FILE* restrict stream);
 int getc(FILE* stream);
 int getchar(void);
-char* gets(char* s);
+char* gets(char* s);  // removed in C++14
 int putc(int c, FILE* stream);
 int putchar(int c);
 int puts(const char* s);
@@ -158,7 +158,9 @@
 using ::fputs;
 using ::getc;
 using ::getchar;
+#if _LIBCPP_STD_VER <= 11
 using ::gets;
+#endif
 using ::putc;
 using ::putchar;
 using ::puts;