gij/gcj has some JDK1.5 classes in it, but it only supports JDK1.4 as the default source level.  This confuses older ant versions and our build script tries to compile a JDK1.5 version.  Instead of letting ant detect the java version, let the jvm tell us that itself using java.specification.version as suggested by Heikki Linnakangas. Also put in a check for a JDK1.6 compile attempt and bail out with an explanatory unsupported error message instead of just failing at some random point.
gij/gcj has some JDK1.5 classes in it, but it only supports JDK1.4
as the default source level.  This confuses older ant versions and
our build script tries to compile a JDK1.5 version.  Instead of
letting ant detect the java version, let the jvm tell us that itself
using java.specification.version as suggested by Heikki Linnakangas.
Also put in a check for a JDK1.6 compile attempt and bail out with
an explanatory unsupported error message instead of just failing
at some random point.

element-doo/postgresql-jdbc,element-doo/postgresql-jdbc