coroutines: Rename the coroutines cpp builtin.

The current standard draft (n4861) amends the cpp builtin for
coroutines to '__cpp_impl_coroutine', no other change.

gcc/c-family/ChangeLog:

2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>

	* c-cppbuiltin.c (c_cpp_builtins): Update coroutines builtin
	define, per n4861.

gcc/testsuite/ChangeLog:

2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>

	* g++.dg/coroutines/coro-pre-proc.C: Update coroutines builtin
	define, per n4861.
	* g++.dg/coroutines/coro.h: Likewise.

libstdc++-v3/ChangeLog:

2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>

	* include/std/coroutine: Update coroutines builtin define,
	per n4861.

gcc/c-family/ChangeLog

@@ -1,3 +1,8 @@
+2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* c-cppbuiltin.c (c_cpp_builtins): Update coroutines builtin
+	define, per n4861.
+
 2020-04-02  Richard Biener  <rguenther@suse.de>
 
 	PR c/94392

gcc/c-family/c-cppbuiltin.c

@@ -1012,7 +1012,7 @@ c_cpp_builtins (cpp_reader *pfile)
             cpp_define (pfile, "__cpp_concepts=201507L");
         }
       if (flag_coroutines)
-	cpp_define (pfile, "__cpp_coroutines=201902L"); /* n4835, C++20 CD */
+	cpp_define (pfile, "__cpp_impl_coroutine=201902L"); /* n4861, DIS */
       if (flag_tm)
 	/* Use a value smaller than the 201505 specified in
 	   the TS, since we don't yet support atomic_cancel.  */

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* g++.dg/coroutines/coro-pre-proc.C: Update coroutines builtin
+	define, per n4861.
+	* g++.dg/coroutines/coro.h: Likewise.
+
 2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>
 
 	* gcc.dg/darwin-version-1.c: Use -mmacosx-version-min= 10.8

gcc/testsuite/g++.dg/coroutines/coro-pre-proc.C

@@ -1,9 +1,9 @@
 // Only need to compile this, with the default options from the .exp.
 
-#ifndef __cpp_coroutines
+#ifndef __cpp_impl_coroutine
 #error "coroutines should engaged."
 #endif
 
-#if __cpp_coroutines != 201902L
+#if __cpp_impl_coroutine != 201902L
 #error "coroutine version out of sync."
 #endif

gcc/testsuite/g++.dg/coroutines/coro.h

@@ -29,7 +29,7 @@ namespace coro = std::experimental;
 // Fragments (with short-cuts) to mimic enough of the library header to
 // make some progress.
 
-#  if __cpp_coroutines
+#  if __cpp_impl_coroutine
 
 namespace std {
 inline namespace __n4835 {

libstdc++-v3/ChangeLog

@@ -1,3 +1,8 @@
+2020-04-13  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* include/std/coroutine: Update coroutines builtin define,
+	per n4861.
+
 2020-04-09  Jonathan Wakely  <jwakely@redhat.com>
 
 	* libsupc++/compare (compare_three_way): Fix noexcept-specifier.

libstdc++-v3/include/std/coroutine

@@ -54,7 +54,7 @@ namespace std _GLIBCXX_VISIBILITY (default)
 {
   _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
-#if __cpp_coroutines
+#if __cpp_impl_coroutine
   inline namespace __n4835 {
 
   // 17.12.2 coroutine traits