Message recall window extensions

by <Someone>

(the following text accompanies the patch at <Someone>'s web page)

add more configurability to the new msg_window option of [..]3.4.0.
It allows the configuration option to take an optional parameter to
specify the style of message history display to use.

allows the following configuration options:

msg_window:s - single message (as was the default in 3.3.0)
msg_window:c - combination; two messages in 'single', then as 'full'
msg_window:f - full window; oldest message first
msg_window:r - full window reversed; newest message first

In the event of no parameter being provided,
the patch is compatible with the current 3.4.0 behaviour:
msg_window = 'full'
!msg_window = 'single'
msg_window can be configured for these options in the
Options menu (Shift-O)
msg_window stores the current window type in the non-persistent
iflags structure, which means that savefile/bones files should be
100% compatible with Vanilla, but at the disadvantage that your
customisations to msg_window will be replaced with your
defaults.nh (or ~/.nethackrc) value every time you restart a saved game.
Credits:

The patch draws inspiration (and code snippets) extensively
from <Someone>'s original msg_window patch, [...] as well as <Someone>'s code for reverse ordering implemented until recently in
Slash'em.

win/tty/getline.c

@@ -72,7 +72,7 @@ getlin_hook_proc hook;
 		    *bufp = 0;
 		}
 		if(c == '\020') { /* ctrl-P */
-		    if (iflags.prevmsg_window) {
+		    if (iflags.prevmsg_window != 's') {
 			int sav = ttyDisplay->inread;
 			ttyDisplay->inread = 0;
 			(void) tty_doprev_message();
@@ -90,7 +90,7 @@ getlin_hook_proc hook;
 			doprev = 1;
 			continue;
 		    }
-		} else if (doprev && !iflags.prevmsg_window) {
+		} else if (doprev && iflags.prevmsg_window == 's') {
 		    tty_clear_nhwindow(WIN_MESSAGE);
 		    cw->maxcol = cw->maxrow;
 		    doprev = 0;