Merge with Ubuntu (Closes: #708985)

- control: Depend on default-jre | java2-runtime
- Ensure backwards compatible bytecode is built (LP: #1049777):
  + p/autoconf-enable-javacflags.patch: Update autoconf configuration
    to support use of JAVACFLAGS during build process.
  + rules: Supply JAVACFLAGS to ensure source/target is set to 1.5.