c++: Add test for PR 93901.

gcc/testsuite/g++.dg/cpp0x/noexcept57.C

+// PR c++/93901
+// { dg-do compile { target c++11 } }
+
+void *operator new (__SIZE_TYPE__, void *p) noexcept { return p; }
+
+extern void *mem;
+
+constexpr bool YES = true;
+
+struct NoexceptTrueCtor {
+	NoexceptTrueCtor() noexcept(true);
+};
+void NoexceptTrueFun() noexcept(true);
+
+struct NoexceptYesCtor {
+	NoexceptYesCtor() noexcept(YES);
+};
+void NoexceptYesFun() noexcept(YES);
+
+struct NoexceptOneEqOneCtor {
+	NoexceptOneEqOneCtor() noexcept(1 == 1);
+};
+void NoexceptOneEqOneFun() noexcept(1 == 1);
+
+struct NoNoexceptCtor {
+	NoNoexceptCtor();
+};
+void NoNoexceptFun();
+
+static_assert(noexcept(new(mem) NoexceptTrueCtor), "2"); // OK
+static_assert(noexcept(NoexceptTrueFun()), "3"); // OK
+
+static_assert(noexcept(new(mem) NoexceptYesCtor), "5"); // fail
+static_assert(noexcept(NoexceptYesFun()), "6"); // OK
+
+static_assert(noexcept(new(mem) NoexceptOneEqOneCtor), "8"); // fail
+static_assert(noexcept(NoexceptOneEqOneFun()), "9"); // OK
+
+static_assert(!noexcept(new(mem) NoNoexceptCtor), "11"); // OK
+static_assert(!noexcept(NoNoexceptFun()), "12"); // OK