attrcurse() on 'see invisible'

If hero has intrinsic see-invisible and a gremlin steals that, the
map wasn't being updated to hide invisible monsters (until the next
iteration of moveloop() after other monsters finished current turn).

src/sit.c

@@ -479,6 +479,12 @@ attrcurse(void)
     case 7:
         if (HSee_invisible & INTRINSIC) {
             HSee_invisible &= ~INTRINSIC;
+            if (!See_invisible) {
+                set_mimic_blocking();
+                see_monsters();
+                /* might not be able to see self anymore */
+                newsym(u.ux, u.uy);
+            }
             You("%s!", Hallucination ? "tawt you taw a puttie tat"
                                      : "thought you saw something");
             break;