renamed display to output

src/potion.cc

@@ -43,7 +43,7 @@ potion &potion::operator=(potion &&p) {
         return *this;
 }
 
-void potion::print(display *out) {
+void potion::print(output *out) {
         out->print_char(pos, 'P', COLOR_PAIR(COLOR_GREEN));
 }