Allow TTY text windows to be scrolled backwards

The following keys now work in multi-page text windows:

 - '<' previous page
 - '>' next page
 - '^' first page
 - '|' last page

This means that text windows can be scrolled backwards in the TTY
windowport, for the first time ever, meaning help screens are actually
helpful now... at least for players who are aware of these menu-style
page controls to begin with (an issue of its own right).

Preserves save compatibility.
Interrupt multi-turn actions when HP/Pw is restored, enhanced

Ported from UnNetHack.

e.g. If you're hurt, do '100.' and heal to full in 20 turns, you'll be
stopped after 20 turns instead of waiting the full 100.  Enhancements
compared to UnNetHack:

 - Can be toggled with the new 'interrupt_hp_pw' option.
 - Will never interrupt running or travel.

Preserves save compatibility.
Stop running/travel when becoming hungry/weak from hunger

Ported from DynaHack.

Preserves save compatibility.
Fix the infinite travel bug

See comment in code for details.

Preserves save compatibility.