Pass #1 at localizing assumptions about fixed layout and

handling non-fixed layouts.

This uncovered a bug where we weren't rounding up the header
size to the element alignment when allocating an array of archetypes.

Writing up a detailed test case for *that* revealed that we were
never initializing the length field of heap arrays.  Fixing that
caused a bunch of tests to crash trying to release stuff.  So...
I've left this in a workaround state right now because I have to
catch a plane.

Swift SVN r4804

lib/IRGen/GenObjC.cpp

@@ -29,7 +29,6 @@
 #include "CallEmission.h"
 #include "Cleanup.h"
 #include "Explosion.h"
-#include "FixedTypeInfo.h"
 #include "FormalType.h"
 #include "FunctionRef.h"
 #include "GenClass.h"
@@ -1415,4 +1414,4 @@ bool irgen::requiresObjCPropertyDescriptor(VarDecl *property) {
   if (auto override = property->getOverriddenDecl())
     return requiresObjCPropertyDescriptor(override);
   return false;
-}
+}