[Java] Add Travis matrix of Java builds for 8 and 11.

Author: mjpt777

.travis.yml

@@ -7,14 +7,34 @@ sudo: false
 matrix:
  include:
 
- # Java linux build
- - name: "Java 8"
+ - name: "Oracle Java 8"
  language: java
  jdk: oraclejdk8
  os: linux
  script:
  - ./gradlew
 
+ - name: "Oracle Java 11"
+ language: java
+ jdk: oraclejdk11
+ os: linux
+ script:
+ - ./gradlew
+
+ - name: "OpenJDK 8"
+ language: java
+ jdk: openjdk8
+ os: linux
+ script:
+ - ./gradlew
+
+ - name: "OpenJDK 11"
+ language: java
+ jdk: openjdk11
+ os: linux
+ script:
+ - ./gradlew
+
  # clang-4
  - env: COMPILER=clang++-4.0
  compiler: clang