[osx] Annotation tooltips

Annotations can optionally have tooltips. osxapp has an option, off by default, to assign a (localized) tooltip to each dropped pin.

include/mbgl/darwin/MGLAnnotation.h

@@ -1,5 +1,6 @@
 #import <Foundation/Foundation.h>
 #import <CoreLocation/CoreLocation.h>
+#import <TargetConditionals.h>
 
 #import "MGLTypes.h"
 
@@ -29,6 +30,13 @@ NS_ASSUME_NONNULL_BEGIN
 *   This string is displayed in the callout for the associated annotation. */
 @property (nonatomic, readonly, copy, nullable) NSString *subtitle;
 
+#if !TARGET_OS_IPHONE
+
+/** The string containing the annotation’s tooltip. */
+@property (nonatomic, readonly, copy, nullable) NSString *toolTip;
+
+#endif
+
 @end
 
 NS_ASSUME_NONNULL_END

include/mbgl/darwin/MGLShape.h

@@ -15,6 +15,13 @@ NS_ASSUME_NONNULL_BEGIN
 /** The subtitle of the shape annotation. The default value of this property is `nil`. */
 @property (nonatomic, copy, nullable) NSString *subtitle;
 
+#if !TARGET_OS_IPHONE
+
+/** The tooltip of the shape annotation. The default value of this property is `nil`. */
+@property (nonatomic, copy, nullable) NSString *toolTip;
+
+#endif
+
 @end
 
 NS_ASSUME_NONNULL_END