Replace __cplusplus comparisons and dialect __has_feature checks with TEST_STD_VER.

This is a huge cleanup that helps make the libc++ test suite more portable.
Patch from STL@microsoft.com. Thanks STL!


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@272716 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/basic.string/string.nonmembers/string.io/get_line.pass.cpp

@@ -48,7 +48,7 @@ int main()
         assert(in.eof());
         assert(s == L"   ghij");
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         std::istringstream in(" abc\n  def\n   ghij");

test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim.pass.cpp

@@ -54,7 +54,7 @@ int main()
         assert(in.eof());
         assert(s == L"   ghij");
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         std::istringstream in(" abc*  def**   ghij");

test/std/strings/basic.string/string.nonmembers/string.io/get_line_delim_rv.pass.cpp

@@ -33,7 +33,7 @@ int main()
         getline(std::wistringstream(L" abc*  def*   ghij"), s, L'*');
         assert(s == L" abc");
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         S s("initial text");

test/std/strings/basic.string/string.nonmembers/string.io/get_line_rv.pass.cpp

@@ -33,7 +33,7 @@ int main()
         getline(std::wistringstream(L" abc\n  def\n   ghij"), s);
         assert(s == L" abc");
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         S s("initial text");

test/std/strings/basic.string/string.nonmembers/string.io/stream_extract.pass.cpp

@@ -66,7 +66,7 @@ int main()
         in >> s;
         assert(in.fail());
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         std::istringstream in("a bc defghij");

test/std/strings/basic.string/string.nonmembers/string.io/stream_insert.pass.cpp

@@ -52,7 +52,7 @@ int main()
         assert(out.good());
         assert(L"   " + s == out.str());
     }
-#if __cplusplus >= 201103L
+#if TEST_STD_VER >= 11
     {
         typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
         std::basic_ostringstream<S::value_type, S::traits_type, S::allocator_type> out;