Message recall window extensions

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.