bug fix, segfaults and sickness caused by `plot'

ChangeLog

@@ -1,3 +1,10 @@
+2010-08-04  Robert Larice
+ * src/frontend/control.c :
+    fix an ancient bug, trampling on freed memory causing segfaults and sickness.
+    getlims() {a function used by plot} does surgery to a wordlist,
+      freeing some words.
+    yet docommand() relied on the wordlist being unmodified.
+
 2010-08-02  Robert Larice
  * src/frontend/hpgl.c ,
  * src/frontend/plotting/plot5.c :

src/frontend/control.c

@@ -239,8 +239,10 @@ docommand(wordlist *wlist)
         /* Now fix the pointers and advance wlist. */
     out:        wlist->wl_prev = ee;
         if (nextc) {
-            if (nextc->wl_prev)
-                nextc->wl_prev->wl_next = nextc;
+            for(wl=wlist; wl->wl_next; wl=wl->wl_next)
+                ;
+            wl->wl_next = nextc;
+            nextc->wl_prev = wl;
             wlist = nextc->wl_next;
         }
     } while (nextc && wlist);