Honor __unaligned in codegen for declarations and expressions

This patch honors the unaligned type qualifier (currently available through he
keyword __unaligned and -fms-extensions) in CodeGen. In the current form the
patch affects declarations and expressions. It does not affect fields of
classes.

Differential Revision: https://reviews.llvm.org/D30166

llvm-svn: 297276
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index ae8a636..a1b508f7 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5677,6 +5677,8 @@
     T = Ref->getPointeeType();
 
   // __alignof is defined to return the preferred alignment.
+  if (T.getQualifiers().hasUnaligned())
+    return CharUnits::One();
   return Info.Ctx.toCharUnitsFromBits(
     Info.Ctx.getPreferredTypeAlign(T.getTypePtr()));
 }