cmath: Support clang's -fdelayed-template-parsing

r283051 added some functions to cmath (in namespace std) that have the
same name as functions in math.h (in the global namespace).  Clang's
limited support for `-fdelayed-template-parsing` chokes on this.  Rename
the ones in `cmath` and their uses in `complex` and the test.

rdar://problem/32848355

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@307357 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/numerics/c.math/constexpr-fns.pass.cpp

@@ -23,9 +23,9 @@
 
 #include <cmath>
 
-static_assert(std::__libcpp_isnan(0.) == false, "");
-static_assert(std::__libcpp_isinf(0.0) == false, "");
-static_assert(std::__libcpp_isfinite(0.0) == true, "");
+static_assert(std::__libcpp_isnan_or_builtin(0.) == false, "");
+static_assert(std::__libcpp_isinf_or_builtin(0.0) == false, "");
+static_assert(std::__libcpp_isfinite_or_builtin(0.0) == true, "");
 
 int main()
 {

test/libcxx/numerics/c.math/fdelayed-template-parsing.sh.cpp

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// test that cmath builds with -fdelayed-template-parsing
+
+// REQUIRES: fdelayed-template-parsing
+
+// RUN: %build -fdelayed-template-parsing
+// RUN: %run
+
+#include <cmath>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main() {
+  assert(std::isfinite(1.0));
+  assert(!std::isinf(1.0));
+  assert(!std::isnan(1.0));
+}
+
+using namespace std;