[tests] XFAIL a few things that require libc (?) support missing on Darwin.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@174450 91177308-0d34-0410-b5e6-96231b3b80d8

test/depr/depr.c.headers/uchar_h.pass.cpp

@@ -6,6 +6,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: apple-darwin
 
 // <uchar.h>
 

test/language.support/support.start.term/quick_exit.pass.cpp

@@ -6,6 +6,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: apple-darwin
 
 // test quick_exit and at_quick_exit
 

test/strings/c.strings/cuchar.pass.cpp

@@ -6,6 +6,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: apple-darwin
 
 // <cuchar>
 

test/strings/c.strings/version_cuchar.pass.cpp

@@ -6,6 +6,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// XFAIL: apple-darwin
 
 // <cuchar>