main: let the main loop restore the main menu, if needed

Don't make it the responsibility of the executed functions to restore
the list of shortcuts of the edit window.  Just detect whether another
menu was displayed, and if so, redisplay the main menu.

src/files.c

@@ -590,7 +590,6 @@ void switch_to_prevnext_buffer(bool to_next)
 #ifdef DEBUG
     dump_filestruct(openfile->current);
 #endif
-    display_main_list();
 }
 
 /* Switch to the previous entry in the openfile filebuffer. */
@@ -1342,8 +1341,6 @@ void do_insertfile_void(void)
 		FALSE
 #endif
 		);
-
-    display_main_list();
 }
 
 /* When passed "[relative path]" or "[relative path][filename]" in
@@ -2474,8 +2471,6 @@ void do_writeout_void(void)
     /* If the user chose to discard the buffer, close it. */
     if (do_writeout(FALSE) == 2)
 	close_and_go();
-
-    display_main_list();
 }
 
 #ifndef NANO_TINY