RFR [JDK8]: 7169894: JAXP Plugability Layer: using service loader

[Joe Wang]

Hi,

This is a patch to replace the manual process in the 3rd step of the 
JAXP implementation resolution mechanism with ServiceLoader.  Please see 
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7169894 for more 
details about the issue.

Note that FactoryFinder is duplicated for each JAXP subpackage. The ones 
in the following packages are the same:
/jaxp-api/src/javax/xml/datatype/FactoryFinder.java
/jaxp-api/src/javax/xml/parsers/FactoryFinder.java
/jaxp-api/src/javax/xml/stream/FactoryFinder.java
/jaxp-api/src/javax/xml/transform/FactoryFinder.java

The following two are similar except that they perform Schema Language 
or Object Model support check:
/jaxp-api/src/javax/xml/validation/SchemaFactoryFinder.java
/jaxp-api/src/javax/xml/xpath/XPathFactoryFinder.java

It's a bit rush since I have only had time to test regular JDK using JDK 
1.6.0_27.  Further test on jigsaw is needed.
All jaxp unit/SQE tests are passed. But TCK test is still running.  So 
please take this as an initial review.

webrev:
http://cr.openjdk.java.net/~joehw/jdk8/7169894/webrev/

Thanks,
Joe