#include <test_macros.h> in all the regex tests, and remove all mentions of __cpluplus (use TEST_STD_VERS and/or XFAIL instead). No functional change

llvm-svn: 267567
diff --git a/libcxx/test/std/re/re.regex/re.regex.assign/assign.pass.cpp b/libcxx/test/std/re/re.regex/re.regex.assign/assign.pass.cpp
index 9c5f834..988d555 100644
--- a/libcxx/test/std/re/re.regex/re.regex.assign/assign.pass.cpp
+++ b/libcxx/test/std/re/re.regex/re.regex.assign/assign.pass.cpp
@@ -16,6 +16,7 @@
 
 #include <regex>
 #include <cassert>
+#include "test_macros.h"
 
 int main()
 {