[libc++] Tolerate presence of __deallocate macro

Summary:
On Windows the identifier `__deallocate` is defined as a macro by one of the Windows system headers. Previously libc++ worked around this by `#undef __deallocate` and generating a warning. However this causes the WIN32 version of `__threading_support` to always generate a warning on Windows. This is not OK.

This patch renames all usages of `__deallocate` internally as to not conflict with the macro.

Reviewers: mclow.lists, majnemer, rnk, rsmith, smeenai, compnerd

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28426

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291332 91177308-0d34-0410-b5e6-96231b3b80d8

include/valarray

@@ -348,7 +348,6 @@ template <class T> unspecified2 end(const valarray<T>& v);
 #include <new>
 
 #include <__undef_min_max>
-#include <__undef___deallocate>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -3697,7 +3696,7 @@ valarray<_Tp>::resize(size_t __n, value_type __x)
     {
         while (__end_ != __begin_)
             (--__end_)->~value_type();
-        _VSTD::__deallocate(__begin_);
+        _VSTD::__libcpp_deallocate(__begin_);
         __begin_ = __end_ = nullptr;
     }
     if (__n)