rogue4: fix most GCC5 warnings.

Converting all function definitions to ANSI style accounts for most of
the change.  This has exposed other problems, such as daemons not
actually being their stated type, that will require more careful
solutions.

rogue4/potions.c

@@ -17,7 +17,8 @@
  * quaff:
  *	Quaff a potion from the pack
  */
-quaff()
+void
+quaff(void)
 {
     register THING *obj, *th;
     register bool discardit = FALSE;
@@ -203,7 +204,8 @@ quaff()
  * invis_on:
  *	Turn on the ability to see invisible
  */
-invis_on()
+void
+invis_on(void)
 {
     register THING *th;
 
@@ -220,8 +222,8 @@ invis_on()
  * see_monst:
  *	Put on or off seeing monsters on this level
  */
-turn_see(turn_off)
-register bool turn_off;
+bool
+turn_see(bool turn_off)
 {
     register THING *mp;
     register bool can_see, add_new;