When declaring an ObjC interface decl with a @compatibility_alias alias name, change the class name to the "real" one.

If we have something like

  @class NewImage;
  @compatibility_alias OldImage NewImage;
  @class OldImage;

the lookup for 'OldImage' will return the 'NewImage' decl ("@class NewImage").
In such a case, when creating the decl for "@class OldImage" use the real declaration name ("NewImage"),
instead of the alias one ("OldImage"), otherwise we will break IdentifierResolver and redecls-chain invariants.

Fixes crash of rdar://14112291.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184238 91177308-0d34-0410-b5e6-96231b3b80d8