Build fixes.

1. Fixed polyglot antrun build, at least to work on JDK 1.7 on Mac.
2. Made cast.js.rhino point to Rhino 1.7R3.
Merge pull request #3 from msridhar/smallfixes

Build fixes.
 [releng] Make it possible to build patched versions of WALA

To use, simply place your patches in WALA/patches and adapt
WALA/pom.xml accordingly. Then run "mvn -N patch:apply" *prior*
to your normal "mvn clean install".