fix: use of @optional directive in protocols and interfaces

[t0rr3sp3dr0]

The @optional directive of Objective-C defines that all property and method definitions bellow it are optional. This only changes if a @required directive is placed bellow it. go-macho doesn't implement this properly and mistakenly declares required methods as optional.

Additionally, @required and @optional should only ever be used inside @protocol blocks. But go-macho also uses them in @interface blocks.

This patch fixes both issues.

As I have tweaked the formatting of generated code slightly, I also changed the formatting of categories to keep consistency.

Before:

@protocol UIActivityItemsConfigurationReading <NSObject>

@property (readonly, copy, nonatomic) NSArray *itemProvidersForActivityItemsConfiguration;
@optional
@property (readonly, copy, nonatomic) NSArray *applicationActivitiesForActivityItemsConfiguration;

/* instance methods */
- (id)itemProvidersForActivityItemsConfiguration;
@optional
/* instance methods */
- (id)activityItemsConfigurationMetadataForItemAtIndex:(long long)index key:(id)key;
- (id)activityItemsConfigurationMetadataForKey:(id)key;
- (id)activityItemsConfigurationPreviewForItemAtIndex:(long long)index intent:(id)intent suggestedSize:(struct CGSize { double x0; double x1; })size;
- (id)applicationActivitiesForActivityItemsConfiguration;
- (char)activityItemsConfigurationSupportsInteraction:(id)interaction;
@end

After:

@protocol UIActivityItemsConfigurationReading <NSObject>

@required

@property (readonly, copy, nonatomic) NSArray *itemProvidersForActivityItemsConfiguration;

/* required instance methods */
- (id)itemProvidersForActivityItemsConfiguration;

@optional

@property (readonly, copy, nonatomic) NSArray *applicationActivitiesForActivityItemsConfiguration;

/* optional instance methods */
- (id)activityItemsConfigurationMetadataForItemAtIndex:(long long)index key:(id)key;
- (id)activityItemsConfigurationMetadataForKey:(id)key;
- (id)activityItemsConfigurationPreviewForItemAtIndex:(long long)index intent:(id)intent suggestedSize:(struct CGSize { double x0; double x1; })size;
- (id)applicationActivitiesForActivityItemsConfiguration;
- (char)activityItemsConfigurationSupportsInteraction:(id)interaction;

@end

[blacktop]

LGTM