[Android] build libcore.io.memory.jar using java 6 as source and target

Author: csoroiu

build.xml

@@ -274,7 +274,7 @@
  <target name="androidlibcore:build" depends="-android:init" description="Build the jar containin libcore.io.Memory class">
  <sequential>
  <javac srcdir="${dir.main.android.src}" destdir="${dir.main.android.libcore.build}" includeAntRuntime="false" debug="true"
- bootclasspath="${android.bootclasspath}">
+ bootclasspath="${android.bootclasspath}" source="1.6" target="1.6">
  <include name="libcore/**/*.java"/>
  <compilerarg value="-Xlint:unchecked"/>
  <compilerarg value="-XDignore.symbol.file"/>