Revert r336159, r336157. Some bots failed on qualified std::max_align_t, and other on unqualified max_align_t.

I'll take another stab at this tomorrow. Any ideas for fixing this would be appreciated!

http://lab.llvm.org:8011/builders/lld-x86_64-darwin13/builds/23071/steps/build_Lld/logs/stdio
http://lab.llvm.org:8011/builders/clang-with-thin-lto-ubuntu/builds/11185/steps/build-stage1-compiler/logs/stdio

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336162 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Demangle/ItaniumDemangle.cpp

@@ -17,7 +17,6 @@
 #include <cassert>
 #include <cctype>
 #include <cstdio>
-#include <cstddef>
 #include <cstdlib>
 #include <cstring>
 #include <numeric>
@@ -1951,7 +1950,7 @@ class BumpPointerAllocator {
   static constexpr size_t AllocSize = 4096;
   static constexpr size_t UsableAllocSize = AllocSize - sizeof(BlockMeta);
 
-  alignas(max_align_t) char InitialBuffer[AllocSize];
+  alignas(16) char InitialBuffer[AllocSize];
   BlockMeta* BlockList = nullptr;
 
   void grow() {