Typecheck within assert and assume statements

For example, assert(some_string_literal!=null) would not work previously

Author: smowton

src/java_bytecode/java_bytecode_typecheck_code.cpp

@@ -67,4 +67,8 @@ void java_bytecode_typecheckt::typecheck_code(codet &code)
         a_it++)
       typecheck_expr(*a_it);
   }
+  else if(statement==ID_assert || statement==ID_assume)
+  {
+    typecheck_expr(code.op0());
+  }
 }