update for sunos4 acc compiler

cig/libcig.c

@@ -68,7 +68,7 @@ scheme_value df_c_veclen(long nargs, scheme_value *args)
 
 scheme_value df_free(long nargs, scheme_value *args)
 {
-    extern void free(void* );
+    
 
     cig_check_nargs(1, nargs, "free");
     free((void* )AlienVal(args[0]));

cig/libcig.scm

@@ -123,7 +123,8 @@
     (mapv! string-carrier->string-no-free vec)))
 
 
-(define-foreign C-free (free ((C void*) ptr)) ignore)
+(define-foreign C-free (free ((C void*) ptr)) no-declare ; for SunOS 4.x 
+  ignore)
 
 (define-foreign %set-string-vector-carriers!
   (set_strvec_carriers (vector-desc svec) ((C char**) cvec))