Retire llvm::alignOf in favor of C++11 alignof.

No functionality change intended.

llvm-svn: 284730
diff --git a/clang/lib/CodeGen/CGCleanup.h b/clang/lib/CodeGen/CGCleanup.h
index 98d01b1..2166490 100644
--- a/clang/lib/CodeGen/CGCleanup.h
+++ b/clang/lib/CodeGen/CGCleanup.h
@@ -427,8 +427,7 @@
 // EHCleanupScope ought to have alignment equal to that -- not more
 // (would be misaligned by the stack allocator), and not less (would
 // break the appended classes).
-static_assert(llvm::AlignOf<EHCleanupScope>::Alignment ==
-                  EHScopeStack::ScopeStackAlignment,
+static_assert(alignof(EHCleanupScope) == EHScopeStack::ScopeStackAlignment,
               "EHCleanupScope expected alignment");
 
 /// An exceptions scope which filters exceptions thrown through it.