"Listing mode" dialog: remove old code

[mooffie]

This patch removes ancient code in the callback of the "Listing mode" dialog.

Three sections are removed. Let's explain each, from the "easiest" to the "hardest":

• The if (g_ascii_tolower (parm) == listing_user_hotkey) section served in the past to move the focus to the input box whenever the "User defined" radio is chosen. This feature stopped working with commit 04b4194371 (2003-Nov-27; a bug was introduced: two different widgets cannot both have the focus), and commit 80d34ca625 further eviscerated it (2010-Jun-29; the focus intention was forgotten). This feature doesn't seem worth it (we don't use this UI pattern elsewhere) so it's best not to re-introduce it.

As for the MSG_KEY sections:

• The two if (widget_is_active (wi)) { h->ret_value = B_USER + n; ... } blocks serve nothing. The git history doesn't go as far back to explain them.

• The if (widget_is_active (wi)) { ... input_assign_text (in, status_format...) ... } section needs to go for two reasons: (1) There are 4 formats for the mini status (one for each listing mode). This section, together with a section in MSG_FOCUS (which was removed in commit 80d34ca625) was the old way of updating the input box to reflect the choice in the radios. But we replaced this mechanism by that of the radio's notification (see the MSG_ACTION case). (2) This section introduces a bug: it overwrites the mini status format the user has typed.

[mooffie]

(I updated the patch to also remove the code that finds the hotkey of "&User defined:")

[andrew_b]

Applied as [ca28e59d081996d40176ade2c367669964408dd7].