Omit @objcImpl from module interfaces

Module interfaces should not include the @objcImplementation attribute, member implementations that are redundant with the ObjC header, or anything that would be invalid in an ordinary extension (e.g. overridden initializers, stored Swift-only properties).

test/ModuleInterface/Inputs/objc_implementation/objc_implementation.h

@@ -0,0 +1,41 @@
+#import <Foundation/Foundation.h>
+
+@interface ImplClass: NSObject
+
+- (nonnull instancetype)init;
+
+@property (assign) int implProperty;
+
+- (void)mainMethod:(int)param;
+
+@end
+
+
+@interface ImplClass (Category1)
+
+- (void)category1Method:(int)param;
+
+@end
+
+
+@interface ImplClass (Category2)
+
+- (void)category2Method:(int)param;
+
+@end
+
+
+@interface NoImplClass
+
+- (void)noImplMethod:(int)param;
+
+@end
+
+@interface NoInitImplClass: NSObject
+
+@property (readonly, strong, nonnull) NSString *s1;
+@property (strong, nonnull) NSString *s2;
+@property (readonly, strong, nonnull) NSString *s3;
+@property (strong, nonnull) NSString *s4;
+
+@end