Make the build system aware of the 1.7 JDK (which icedtea reports itself as) and add an explicit check and complaint if we find a JDK that we don't support.
Make the build system aware of the 1.7 JDK (which icedtea reports
itself as) and add an explicit check and complaint if we find a JDK
that we don't support.

tivv/davepgjdbc,tivv/davepgjdbc