libstdc++: Fix errors from Library Fundamentals TS headers in C++11 [PR 98319]

Currently the <experimental/random>, <experimental/source_location> and
<experimental/utility> headers can be included in C++98 and C++11 modes,
but gives errors. With this change they can be included, but define
nothing.

libstdc++-v3/ChangeLog:

	PR libstdc++/98319
	* include/experimental/random: Only define contents for C++14
	and later.
	* include/experimental/source_location: Likewise.
	* include/experimental/utility: Likewise.
	* testsuite/experimental/feat-lib-fund.cc: Include all LFTS
	headers that are present. Allow test to run for all modes.

libstdc++-v3/include/experimental/random

@@ -30,6 +30,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_RANDOM
 #define _GLIBCXX_EXPERIMENTAL_RANDOM 1
 
+#if __cplusplus >= 201402L
 #include <random>
 #include <experimental/bits/lfts_config.h>
 
@@ -78,4 +79,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_RANDOM

libstdc++-v3/include/experimental/source_location

@@ -30,6 +30,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_SRCLOC
 #define _GLIBCXX_EXPERIMENTAL_SRCLOC 1
 
+#if __cplusplus >= 201402L
 #include <cstdint>
 
 namespace std {
@@ -84,4 +85,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_SRCLOC

libstdc++-v3/include/experimental/utility

@@ -30,6 +30,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_UTILITY
 #define _GLIBCXX_EXPERIMENTAL_UTILITY 1
 
+#if __cplusplus >= 201402L
 #include <utility>
 #include <bits/uses_allocator.h>
 #include <experimental/bits/lfts_config.h>
@@ -47,4 +48,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_UTILITY

libstdc++-v3/testsuite/experimental/feat-lib-fund.cc

@@ -1,57 +1,36 @@
-// { dg-do preprocess { target c++14 } }
+// { dg-do preprocess }
 
-#if !__has_include(<experimental/tuple>)
-#  error "<experimental/tuple>"
+// Include all the LFTS headers. This should work with any -std flag.
+
+#include <experimental/algorithm>
+#include <experimental/any>
+#include <experimental/array>
+#include <experimental/chrono>
+#include <experimental/deque>
+#include <experimental/forward_list>
+#include <experimental/functional>
+#if __has_include(<experimental/future>) // not supported as of GCC 11
+# include <experimental/future>
 #endif
-
-#if !__has_include(<experimental/type_traits>)
-#  error "<experimental/type_traits>"
-#endif
-
-#if !__has_include(<experimental/ratio>)
-#  error "<experimental/ratio>"
-#endif
-
-#if !__has_include(<experimental/chrono>)
-#  error "<experimental/chrono>"
-#endif
-
-#if !__has_include(<experimental/system_error>)
-#  error "<experimental/system_error>"
-#endif
-
-#if !__has_include(<experimental/functional>)
-#  error "<experimental/functional>"
-#endif
-
-#if !__has_include(<experimental/optional>)
-#  error "<experimental/optional>"
-#endif
-
-#if !__has_include(<experimental/any>)
-#  error "<experimental/any>"
-#endif
-
-#if !__has_include(<experimental/string_view>)
-#  error "<experimental/string_view>"
-#endif
-
-//#if !__has_include(<experimental/memory>)
-//#  error "<experimental/memory>"
-//#endif
-
-//#if !__has_include(<experimental/memory_resource>)
-//#  error "<experimental/memory_resource>"
-//#endif
-
-//#if !__has_include(<experimental/future>)
-//#  error "<experimental/future>"
-//#endif
-
-#if !__has_include(<experimental/algorithm>)
-#  error "<experimental/algorithm>"
-#endif
-
-//#if !__has_include(<experimental/net>)
-//#  error "<experimental/net>"
-//#endif
+#include <experimental/iterator>
+#include <experimental/list>
+#include <experimental/map>
+#include <experimental/memory>
+#include <experimental/memory_resource>
+#include <experimental/numeric>
+#include <experimental/optional>
+#include <experimental/propagate_const>
+#include <experimental/random>
+#include <experimental/ratio>
+#include <experimental/regex>
+#include <experimental/set>
+#include <experimental/source_location>
+#include <experimental/string>
+#include <experimental/string_view>
+#include <experimental/system_error>
+#include <experimental/tuple>
+#include <experimental/type_traits>
+#include <experimental/unordered_map>
+#include <experimental/unordered_set>
+#include <experimental/utility>
+#include <experimental/vector>