Remove `drop_mode` setting and in-game toggle for `single` behavior

The setting itself went largely unused with a few exceptions for bot
configurations, and the toggle (either @ or Ctrl-D in the drop menu)
added nothing to the interface: It was intransparent and probably not
known to a single player out there. Like with the pickup menu, what was
old `multi` is the far superior interface, and unlike with pickup it
also has been the default for a long time.
For quickly (interface-wise) dropping items, there still exists `D` to
drop your last pickup, but even that is rather prone to input errors.

1 files changed, 0 insertions, 6 deletions

diff --git a/crawl-ref/source/initfile.h b/crawl-ref/source/initfile.h
index 4cab3c0bda..b104483d00 100644
--- a/crawl-ref/source/initfile.h
+++ b/crawl-ref/source/initfile.h
@@ -13,12 +13,6 @@
 #include "itemprop-enum.h"
 #include "unicode.h"
 
-enum drop_mode_type
-{
-    DM_SINGLE,
-    DM_MULTI,
-};
-
 int str_to_summon_type(const string &str);
 string gametype_to_str(game_type type);