Add <span> to <bits/stdc++.h> precompiled header

	* include/precompiled/stdc++.h: Include <span> for C++20.
	* testsuite/17_intro/names.cc: Do not define 'e' for C++20.

From-SVN: r276574

libstdc++-v3/ChangeLog

+2019-10-04  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/precompiled/stdc++.h: Include <span> for C++20.
+	* testsuite/17_intro/names.cc: Do not define 'e' for C++20.
+
 2019-10-03  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* include/parallel/multiway_merge.h (_RAIter3): Replace _C by _Cp.

libstdc++-v3/include/precompiled/stdc++.h

@@ -139,7 +139,7 @@
 // #include <concepts>
 #include <numbers>
 // #include <ranges>
-// #include <span>
+#include <span>
 // #include <syncstream>
 #include <version>
 #endif

libstdc++-v3/testsuite/17_intro/names.cc

@@ -53,7 +53,10 @@
 #endif
 // <queue> and <stack> defined data members called c
 #define d (
+#if __cplusplus <= 201703L
+// <numbers> defines std::numbers::e
 #define e (
+#endif
 #define f (
 #define g (
 #if __cplusplus >= 201402L