[libc++] Add missing #include in C11 features tests

Summary:
These #includes are quite important, since otherwise any

    #if TEST_STD_VER > 14 && defined(TEST_HAS_C11_FEATURES)

checks are always false, and so we don't actually test for C11 support
in the standard library.

Reviewers: mclow.lists, EricWF

Subscribers: christof, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D50674

llvm-svn: 339675

libcxx/test/libcxx/language.support/has_c11_features.pass.cpp

@@ -14,6 +14,9 @@
 //		_LIBCPP_HAS_C11_FEATURES - which is defined in <__config>
 //	They should always be the same
 
+#include <__config>
+#include "test_macros.h"
+
 #ifdef TEST_HAS_C11_FEATURES
 # ifndef _LIBCPP_HAS_C11_FEATURES
 #  error "TEST_HAS_C11_FEATURES is defined, but _LIBCPP_HAS_C11_FEATURES is not"

libcxx/test/std/depr/depr.c.headers/float_h.pass.cpp

@@ -11,6 +11,8 @@
 
 #include <float.h>
 
+#include "test_macros.h"
+
 #ifndef FLT_ROUNDS
 #error FLT_ROUNDS not defined
 #endif

libcxx/test/std/language.support/support.limits/c.limits/cfloat.pass.cpp

@@ -11,6 +11,8 @@
 
 #include <cfloat>
 
+#include "test_macros.h"
+
 #ifndef FLT_ROUNDS
 #error FLT_ROUNDS not defined
 #endif