Set 'Allow app ext API only' for Messages exts

lib/cocoapods/installer/xcode/pods_project_generator.rb

@@ -185,7 +185,7 @@ module Pod
           frameworks_group = project.frameworks_group
           aggregate_targets.each do |aggregate_target|
             is_app_extension = !(aggregate_target.user_targets.map(&:symbol_type) &
-                                 [:app_extension, :watch_extension, :watch2_extension, :tv_extension]).empty?
+                                 [:app_extension, :watch_extension, :watch2_extension, :tv_extension, :messages_extension]).empty?
             is_app_extension ||= aggregate_target.user_targets.any? { |ut| ut.common_resolved_build_setting('APPLICATION_EXTENSION_API_ONLY') == 'YES' }
 
             aggregate_target.pod_targets.each do |pod_target|

spec/unit/installer/xcode/pods_project_generator_spec.rb

@@ -209,6 +209,10 @@ module Pod
               test_extension_target(:tv_extension)
             end
 
+            it 'configures APPLICATION_EXTENSION_API_ONLY for Messages extension targets' do
+              test_extension_target(:messages_extension)
+            end
+
             it 'configures APPLICATION_EXTENSION_API_ONLY for targets where the user target has it set' do
               mock_user_target = mock('UserTarget', :symbol_type => :application)
               mock_user_target.expects(:common_resolved_build_setting).with('APPLICATION_EXTENSION_API_ONLY').returns('YES')