Fix order of deallocations, add heap unit test

Jan Breuer

2016-04-24 7d6b42c51111d450097af396af16a052e52a4442

 libscpi/src/expression.c

@@ -245,6 +245,8 @@
            *dimensions = fromDimensions;
            return SCPI_EXPR_OK;
        }
    } else if (err == SCPI_EXPR_NO_MORE) {
        err = SCPI_EXPR_ERROR;
    }

    return err;