Build failure with Java 11 and --release

[jcflack]

f0bb8b5 (and several later commits) introduced uses of the newFactory methods of javax.xml.stream.XML{Input,Output}Factory. These methods are present in all Java versions we intend to support, back to Java 6. They are documented in the
Java 6 API docs, and can be confirmed with javap in the rt.jar of an IcedTea-6 installation.

There was never a problem until c3b47c9 altered the POM to use javac's --release 6 option when compiling with a 9 to 11 javac, rather than the -source/-target options formerly used. The --release option goes further than checking source compatibility, and checks that all API used was present in the targeted release. To do that, it relies on .sig files (which are really .class files stripped down to only API signatures) that ship in the ct.sym file (which is really a jar) in the JDK's lib directory.

Extracting the 6/javax/xml/stream/XML{In,Out}putFactory.sig files from ct.sym and examining them with javap shows that they are missing the newFactory methods, leading javac to report incorrectly that the methods weren't available in 6.

Building with Java 12 isn't a problem, because it no longer supports Java 6, and the POM already adjusts the --release option in that case to 7, and the methods are not missing from the shipped signatures for 7.

The best fix is probably to change all of the uses to the equivalent newInstance() methods, which are properly found in the .sig files. (There was one newFactory method on XMLOutputFactory that had to be deprecated because of a typo, and a corresponding one in XMLInputFactory that was also deprecated for consistency, but neither of those appears in PL/Java.)

Making a new issue, first reported in a comment on #212.

See also: JEP247

[jcflack]

Believed resolved in 1.5.4.