* eval.c (rt_defvarl): More accurate self string. (rt_defv): New static function: like rt_defvarl but ensures that the new variable has a binding cell, and returns that cell instead of the hash cell. (op_defvarl): Take advantage of rt_defv to not have to cons up the binding cell. (eval_init): Register sys:rt-defv intrinsic. * parser.c (read_file_common): Compiled files are now version 7, so we must recognize them. We still load version 6 files because rt:defvarl still exists for them. * share/txr/stdlib/compiler.tl (expand-defvarl): Improve the generated code in two ways. Firstly, use the new sys:rt-defv, which returns the binding cell, so that the value can be stored into it with rplacd without having to cons up anything. Secondly, if there is no value expression, don't emit the code to do the assignment. (%tlo-ver%): Bump compiled file version to (7 0). * txr.1: Add note about TXR 260 loading version 7 and 6.