Update build

- remove Ant build file
- add Maven compiler plugin and set to Java 8
  (previously used Maven default Java 1.6)
- update Github actions to get rid of build warnings
- Java distribution remains 'azul' which
  was default before (no default now)

.github/workflows/maven.yml

@@ -15,10 +15,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up JDK 1.8
-      uses: actions/setup-java@v1
+    - uses: actions/checkout@v4
+    - name: Set up Java 8 JDK
+      uses: actions/setup-java@v4
       with:
-        java-version: 1.8
+        distribution: 'zulu'
+        java-version: 8
     - name: Build with Maven
       run: mvn -B package --file pom.xml

pom.xml

@@ -56,6 +56,15 @@
   </dependencies>
   <build>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.12.1</version>
+        <configuration>
+          <source>1.8</source>
+          <target>1.8</target>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>