Build: Set javac release property (ticket #2775)

Ant version 1.9.8 or higher now required
Drop support for Xenial package build
Fix up BOB build configuration
Fix i2psnark standalone build

apps/streaming/java/build.xml

@@ -24,6 +24,7 @@
     <!-- only used if not set by a higher build.xml -->
     <property name="javac.compilerargs" value="" />
     <property name="javac.version" value="1.8" />
+    <property name="javac.release" value="8" />
 
     <target name="compile" depends="depend">
         <mkdir dir="./build" />
@@ -31,6 +32,7 @@
         <javac
             srcdir="./src"
             debug="true" deprecation="on" source="${javac.version}" target="${javac.version}"
+            release="${javac.release}"
             includeAntRuntime="false"
             encoding="UTF-8"
             destdir="./build/obj"
@@ -60,6 +62,7 @@
         <javac
             srcdir="./test/junit"
             debug="true" deprecation="on" source="${javac.version}" target="${javac.version}"
+            release="${javac.release}"
             includeAntRuntime="false"
             encoding="UTF-8"
             destdir="./build/obj" >