RFR: 8073519: schemagen does not report errors while generating xsd files

[Aleksej Efimov]

Hello,

Please, review the fix for schemagen regression bug [1] in JDK9: The 
JDK9 (and JDK8 too) version of schemagen doesn't report errors during 
the compilation of the input java file.
The issue was introduced by standalone JAXB project changes and then it 
was synced to JDK source. The SchemaGenerator class was changed to use 
javax.tools.JavaCompiler (instead of com.sun.tools.apt.process), but the 
diagnostic information generated by javac was silently ignored.
The proposed patch solves the reported problem: 
http://cr.openjdk.java.net/~aefimov/8073519/9/00/
The generated messages with fix applied is the same as in JDK7 - same as 
was before mentioned changes.

The proposed fix is already integrated to standalone JAXB project and 
identical to the proposed source changes. Testing shows no failures with 
schemagen tool.

With Best Regards,
Aleksej

[1] https://bugs.openjdk.java.net/browse/JDK-8073519