Inverse (Un) instead of blue bg (NAO) for piles

The most common item material is iron, colored cyan, which is almost
invisible with NAO-style dark blue backgrounds, so use UnNetHack-style
reverse video once more.
Add default msgtype rules

Show --More-- for delayed instadeath messages (credits to stth), plus
hunger and a few others.
Revert "Add autodigdown option"

I was always uncertain about the existence of this option, since it
controlled corner-case behavior and made the options menu even more
intimidating than it already was.

This reverts commit 4bf0151bc2d4f55111c2bb30c88e74d2cf903a91.

Conflicts:

	libnitrohack/include/flag.h
Change delay_msg option into a boolean flag

When this was an integer, the only useful values were 0 (off) and small
numbers, so this change reflects that.
Set hilite_peaceful to true by default

It's better for this to confuse long-time NetHack players by setting
this on by default than for players in general to not realize that this
option even exists otherwise.
Allow option msgheight = 0 for automatic size

The msgheight interface option now allows and defaults to 0 (auto),
filling the message window height to fit the number of rows of the
terminal.

About 18 months ago, I emailed Daniel Thaler, asking a bunch of things
including why the message box height was limited; he replied that he
thought that filling the whole height looked ugly.  I think making
players tweak an option to get a filled window instead of by simply
resizing their window is uglier, hence this new feature.