Add the source file to com.ibm.wala.cast.java.test.data

Previously, I only included the source file in the zip file but just
realized the zip file is auto-generated from the
com.ibm.wala.cast.java.test.data/src folder.
Merge pull request #13 from vazexqi/ASTJavaTypeInference-PrimAndStringOp-bug

Add the test file to com.ibm.wala.cast.java.test.data/src for pull request #12