[libc++] Pair _aligned_malloc with _aligned_free

[smeenai]

Summary

Attempting to pair an _aligned_malloc with a regular free causes heap
corruption. Pairing with _aligned_free is required instead.

Makes the following libc++ tests pass on Windows:

std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t.pass.cpp
std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow.pass.cpp
std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t.pass.cpp
std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow.pass.cpp

[compnerd]

Hah, can't believe we missed that.

libcxx/trunk/src/new.cpp

if (ptr)
         ::free(ptr);
 }
 
 _LIBCPP_WEAK
 void
 operator delete(void* ptr, std::align_val_t) _NOEXCEPT
 {
     if (ptr)
+#if defined(_LIBCPP_MSVCRT)
+        ::_aligned_free(ptr);
+#else
         ::free(ptr);
+#endif
 }
 
 _LIBCPP_WEAK
 void
 operator delete(void* ptr, const std::nothrow_t&) _NOEXCEPT
 {
     ::operator delete(ptr);
 }