UI: building without Python again

Also quiet some warnings.

source/blender/editors/interface/interface.c

@@ -4017,9 +4017,11 @@ uiBut *ui_but_change_type(uiBut *but, eButType new_type)
       UNUSED_VARS_NDEBUG(found_layout);
       ui_button_group_replace_but_ptr(uiLayoutGetBlock(but->layout), old_but_ptr, but);
     }
+#ifdef WITH_PYTHON
     if (UI_editsource_enable_check()) {
       UI_editsource_but_replace(old_but_ptr, but);
     }
+#endif
   }
 
   return but;

source/blender/editors/interface/interface_icons.c

@@ -2425,6 +2425,7 @@ void UI_icon_draw_ex(float x,
 ImBuf *UI_icon_alert_imbuf_get(eAlertIcon icon)
 {
 #ifdef WITH_HEADLESS
+  UNUSED_VARS(icon);
   return NULL;
 #else
   const int ALERT_IMG_SIZE = 256;

source/blender/editors/util/numinput.c

@@ -309,7 +309,7 @@ bool user_string_to_number(bContext *C,
   return success;
 
 #else
-  UNUSED_VARS(C, unit, type);
+  UNUSED_VARS(C, unit, type, use_single_line_error, r_error);
   *r_value = atof(str);
   return true;
 #endif