Merge pull request #2257 from eXist-db/oracle11

enable oracleJDK11 on travis

Author: adamretter

.travis.yml

@@ -7,7 +7,8 @@ matrix:
     - jdk: openjdk9
     - jdk: openjdk10
     - jdk: openjdk11
-#     - jdk: oraclejdk11
+    - jdk: oraclejdk11
+    
     - os: osx
       osx_image: xcode9.2
       env: JAVA_HOME=$(/usr/libexec/java_home)