Migrate a few partest jvm tests to JUnit tests.

Migrated to JUnit the following tests (from test/files/jvm):

   * t0632.scala
   * t1118.scala
   * unittest_xml.scala

None of those tests were dependent on anything jvm specific.
Remove test/files/jvm/backendBugUnapply.scala test.

It doesn't seem to test anything XML-specific and I couldn't trace
what kind of backend problem this test is supposed to guard against.
Migrate partest jvm/xmlstuff.scala test to JUnit.
Migrate partest jvm/xmlpull.scala test to JUnit.
Migrate partest jvm/xmlattr.scala test to JUnit.
Migrate partest jvm/xml04embed.scala test to JUnit.
Migrate partest jvm/xml03syntax.scala test to JUnit.