Fix a code-gen thinko.
A couple of fixes to nqp-jvm-cc frontend.

Can be run as:

    nqp nqp-jvm-cc.nqp --setting=NULL -e "nqp::say('omg jvm!')"

It cross-compiles the NQP code to JVM bytecode, then runs the class
file that is produced. Note, no setting or MOP yet, so it won't do
much at all.