defsymacro must remove special marking.

* eval.c (op_defsymacro): Remove sym from the special
hash, unless compatibility 143 or lower is requested.

* txr.1: Document effects of evaluating defsymacro
if a global variable of the same name exists, and the
behavior in lexical scopes where sym is bound.
Added compatibility notes covering the code change.

1 files changed, 2 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index 6246ac1a..39ee9652 100644
--- a/eval.c
+++ b/eval.c
@@ -1567,6 +1567,8 @@ static val op_defsymacro(val form, val env)
     eval_error(form, lit("let: ~s is not a bindable symbol"), sym, nao);
 
   remhash(top_vb, sym);
+  if (!opt_compat || opt_compat > 143)
+    remhash(special, sym);
   sethash(top_smb, sym, cons(sym, second(args)));
   return sym;
 }