using prefixes via their extended command names

Trying to use #reqmenu/#rush/#run/#fight prefixes by their extended
command names didn't work because rhack()'s post-processing was stuck
dealing with the entry for the '#' key after using doextcmd() to run
any command.  Use a static variable (actually a global one since I put
it into struct g) to notify rhack() of the command that ultimately got
executed.

include/decl.h

@@ -728,6 +728,7 @@ struct instance_globals {
     winid en_win;
     boolean en_via_menu;
     long last_command_count;
+    struct ext_func_tab *ext_tlist; /* info for rhack() from doextcmd() */
 
     /* dbridge.c */
     struct entity occupants[ENTITIES];