Review Request: JDK-8172215 java launcher no longer accepts -cp "" empty string

[Mandy Chung]

http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8172215/webrev.00/

This fixes the regression caused by JDK-8168836 such that java -cp “” would be accepted. It’s surprise that no launcher test covering such test case.  Now it’s added in JavaClassPathTest.

This patch also renames the testlibrary ModuleSourceBuilder to ModuleInfoMaker as Alan suggested.

Mandy