Simplify rhack and parse

AFAICT, we only used the first char of the "command_line" string.
Just turn it into int to hold the key the main input loop parse() got.

Shouldn't have any functional difference.

include/decl.h

@@ -236,7 +236,7 @@ struct instance_globals_c {
     coord clicklook_cc;
     /* decl.c */
     char chosen_windowtype[WINTYPELEN];
-    char command_line[COLNO];
+    int cmd_key; /* parse() / rhack() */
     cmdcount_nht command_count;
     /* some objects need special handling during destruction or placement */
     struct obj *current_wand;  /* wand currently zapped/applied */

include/extern.h

@@ -350,7 +350,7 @@ extern void parseautocomplete(char *, boolean);
 extern void lock_mouse_buttons(boolean);
 extern void reset_commands(boolean);
 extern void update_rest_on_space(void);
-extern void rhack(char *);
+extern void rhack(int);
 extern int doextlist(void);
 extern int extcmd_via_menu(void);
 extern int enter_explore_mode(void);