Fix more missing or incorrect feature test macros

	* include/bits/erase_if.h [__cplusplus > 201703L]
	(__cpp_lib_erase_if): Only define for C++2a.
	* include/std/iterator [__cplusplus >= 201402L && !_GLIBCXX_DEBUG]
	(__cpp_lib_null_iterators): Define.
	* include/std/version [__cplusplus >= 201402L && !_GLIBCXX_DEBUG]
	(__cpp_lib_null_iterators): Define.
	[__cpp_impl_destroying_delete] (__cpp_lib_destroying_delete): Define.

From-SVN: r267937

libstdc++-v3/ChangeLog

 2019-01-15  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/bits/erase_if.h [__cplusplus > 201703L]
+	(__cpp_lib_erase_if): Only define for C++2a.
+	* include/std/iterator [__cplusplus >= 201402L && !_GLIBCXX_DEBUG]
+	(__cpp_lib_null_iterators): Define.
+	* include/std/version [__cplusplus >= 201402L && !_GLIBCXX_DEBUG]
+	(__cpp_lib_null_iterators): Define.
+	[__cpp_impl_destroying_delete] (__cpp_lib_destroying_delete): Define.
+
 	* doc/xml/manual/status_cxx2017.xml: Document P0032R3 and P0307R2
 	status.
 	* include/bits/stl_uninitialized.h (__cpp_lib_raw_memory_algorithms):

libstdc++-v3/include/bits/erase_if.h

@@ -38,7 +38,9 @@ namespace std
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
-#define __cpp_lib_erase_if 201900L
+#if __cplusplus > 201703L
+# define __cpp_lib_erase_if 201900L
+#endif
 
   namespace __detail
   {

libstdc++-v3/include/std/iterator

@@ -67,4 +67,8 @@
 #include <bits/streambuf_iterator.h>
 #include <bits/range_access.h>
 
+#if __cplusplus >= 201402L && ! defined _GLIBCXX_DEBUG // PR libstdc++/70303
+# define __cpp_lib_null_iterators 201304L
+#endif
+
 #endif /* _GLIBCXX_ITERATOR */

libstdc++-v3/include/std/version

@@ -42,6 +42,10 @@
 # define __cpp_lib_uncaught_exceptions 201411L
 #endif
 
+#if __cpp_impl_destroying_delete
+# define __cpp_lib_destroying_delete 201806L
+#endif
+
 #if __cplusplus >= 201103L
 // c++11
 #define __cpp_lib_allocator_is_always_equal 201411
@@ -71,6 +75,9 @@
 #define __cpp_lib_is_final 201402L
 #define __cpp_lib_make_reverse_iterator 201402
 #define __cpp_lib_make_unique 201304
+#ifndef _GLIBCXX_DEBUG // PR libstdc++/70303
+# define __cpp_lib_null_iterators 201304L
+#endif
 #define __cpp_lib_quoted_string_io 201304
 #define __cpp_lib_robust_nonmodifying_seq_ops 201304
 #ifdef _GLIBCXX_HAS_GTHREADS