Load automatic module names correctly

Load the Automatic-Module-Name manifest entry value if it's present (see
http://mail.openjdk.java.net/pipermail/jpms-spec-observers/2017-May/000877.html),
otherwise sanitize the name of the .jar file, throwing out all chars
except alphanumeric, duplicate dots and a version qualifier

compiler/testData/javaModules/automaticModuleNames/automatic-module2/m2/B.java

@@ -0,0 +1,3 @@
+package m2;
+
+public class B {}