nupa_assignment(), express some constness

src/frontend/numparam/numparam.h

@@ -66,7 +66,7 @@ void dico_free_entry(entry_t *);
 bool defsubckt(dico_t *, struct card *, nupa_type categ);
 int findsubckt(dico_t *, char *s);
 bool nupa_substitute(dico_t *, const char *s, char *r);
-bool nupa_assignment(dico_t *, char *s, char mode);
+bool nupa_assignment(dico_t *, const char *s, char mode);
 bool nupa_subcktcall(dico_t *, char *s, char *x, char *inst_name);
 void nupa_subcktexit(dico_t *);
 entry_t *entrynb(dico_t *dico, char *s);

src/frontend/numparam/xpressn.c

@@ -1411,7 +1411,7 @@ getexpress(nupa_type *type, SPICE_DSTRINGPTR tstr_p, const char *s)
 
 
 bool
-nupa_assignment(dico_t *dico, char *s, char mode)
+nupa_assignment(dico_t *dico, const char * const s, char mode)
 /* is called for all 'Param' lines of the input file.
    is also called for the params: section of a subckt .
    mode='N' define new local variable, else global...