configure: simplify JDBC Java requirements
configure: simplify JDBC Java requirements

"MonetDB JDBC currently requires Java >= 1.5, but < 1.6 to build"
is a complex way to say "MonetDB JDBC currently requires Java 1.5 to
build", so just say the latter, and also check that.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb