Test the this argument used when checking a constructor

To ensure the fields of the `this` argument to the a constructor are not
incorrectly nondet initialised before entering the constructor.

Author: thomasspriggs

jbmc/regression/jbmc/constructor2/Constructor2.class

@@ -0,0 +1,5 @@
+class Constructor2 {
+  int myField;
+
+  Constructor2() { assert myField == 0; }
+}

jbmc/regression/jbmc/constructor2/Constructor2.java

@@ -0,0 +1,11 @@
+CORE
+Constructor2.class
+--function 'Constructor2.<init>'
+^EXIT=0$
+^SIGNAL=0$
+^VERIFICATION SUCCESSFUL$
+--
+^warning: ignoring
+--
+Test that a field of a class being constructed is zero initialised before the
+constructor is called, where the function being checked is a constructor.