Travis: Use macOS 10.14 with Xcode 11.2

Closes ticket 32241.

.travis.yml

@@ -103,10 +103,11 @@ addons:
       - asciidoc
       - xmlto
 
-## (OSX only) Use the default OSX image
+## (OSX only) Use a recent macOS image
 ## See https://docs.travis-ci.com/user/reference/osx#os-x-version
-## Default is Xcode 9.4 on macOS 10.13 as of August 2018
-#osx_image: xcode9.4
+## Default is Xcode 9.4 on macOS 10.13 as of October 2019
+## Recent is Xcode 11.2 on macOS 10.14 as of October 2019
+osx_image: xcode11.2
 
 install:
   ## If we're on OSX, configure ccache (ccache is automatically installed and configured on Linux)

changes/ticket32241

+  o Testing (continuous integration):
+    - In Travis, use Xcode 11.2 on macOS 10.14. Closes ticket 32241.