Local variables declared in constructor prologue are not visible to constructor epilogue.

Added a test in 8fad2b6 under [tests/PrologueLocal.jif](https://github.com/apl-cornell/jif/blob/8fad2b6266ce9e394c3c38dd4c56aff9bce6339e/tests/PrologueLocal.jif) demonstrating that local variables declared in the constructor's prologue are not visible in the constructor's epilogue.