[ios] Restored toggleDebug

Restored (but deprecated) a method removed in #3100 to avoid a major version bump.

include/mbgl/ios/MGLMapView.h

@@ -956,7 +956,7 @@ IB_DESIGNABLE
 
 @property (nonatomic, getter=isDebugActive) BOOL debugActive __attribute__((deprecated("Use -debugMask and -setDebugMask:.")));
 
-- (void)cycleDebugOptions __attribute__((deprecated("Use -setDebugMask:.")));
+- (void)toggleDebug __attribute__((deprecated("Use -setDebugMask:.")));
 
 /**
     Empties the in-memory tile cache.

platform/ios/src/MGLMapView.mm

@@ -1697,6 +1697,11 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     return self.debugMask;
 }
 
+- (void)toggleDebug
+{
+    self.debugActive = !self.debugActive;
+}
+
 - (void)resetNorth
 {
     [self resetNorthAnimated:YES];
@@ -1714,11 +1719,6 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     self.camera = camera;
 }
 
-- (void)cycleDebugOptions
-{
-    _mbglMap->cycleDebugOptions();
-}
-
 - (void)emptyMemoryCache
 {
     _mbglMap->onLowMemory();