SILGen: stub out CoreData

One of the SILGen tests uses CoreData.  Provide a stubbed out definition
sufficient for the tests.

Author: compnerd

test/SILGen/Inputs/usr/include/CoreData.h

@@ -0,0 +1,16 @@
+
+@import Foundation;
+
+@interface NSEntityDescription : NSObject
+@end
+
+@interface NSManagedObjectContext : NSObject
+@end
+
+@interface NSManagedObject : NSObject
+- (__kindof NSManagedObject *)initWithEntity:(NSEntityDescription *)entity
+              insertIntoManagedObjectContext:(NSManagedObjectContext *)context;
+@property(nonatomic, readonly, strong) NSEntityDescription *entity;
++ (NSEntityDescription *)entity;
+@end
+

test/SILGen/Inputs/usr/include/module.map

@@ -26,6 +26,10 @@ module AppKit {
   header "AppKit.h"
   export *
 }
+module CoreData {
+  header "CoreData.h"
+  export *
+}
 module Dispatch {
   header "dispatch.h"
   export *