8047776: Add module java.transaction to export API javax.transaction

[Alan Bateman]

This is another update to the module graph, this time it's the quagmire 
of the Java Transaction API, a subset of which is defined for Java SE 
for mapping of CORBA exceptions to RMI exceptions and for the XA support 
in the JDBC API.

The proposal is to create a new module (named java.transaction) that 
exports the API package javax.transaction. EE can provide an upgraded 
version of this module as they need it. For the source code layout then 
this means moving the 3 exceptions that were previously in java.corba 
module to the new module. I've used the opportunity to also move the API 
package javax.transaction.xa to the jdk repo (Lance - I hope you are 
okay with the latter, it's just a bit cleaner/understandable to have all 
of java.sql in the one repo).

The webrevs with the proposed changes are here:
    http://cr.openjdk.java.net/~alanb/8047776/

One annoyance is that exception types don't define a serialVersionUID 
and so don't compile outside of the java.corba module. The right thing 
is to add the SUID of course but that subtly changes the spec in that 
SUID will show up in the serialized form. To avoid getting stuck in the 
mud then I've created a new issue JDK-8068413 to track this (it really 
needs JSR 907 to define the SUID for each of its serialized types) and 
added @SuppressWarnings("serial") to these exceptions.

-Alan