Fix alternate number pad interpretation only working for diagonals

Fix alternate number pad interpretation only working for diagonals

This fixes the issue brought up at https://www.reddit.com/r/nethack/comments/dv3pae/curses_and_the_numberpad/?st=k3hgply6&sh=dbc2bf7d .

I don't know why the "regular" (tty) method doesn't seem to work for him,
but I'm going to chalk it up to a PDCurses oddity. What I do know, however,
is that the alternate method I added a year ago or maybe longer, that allows
numpad usage even with number_pad:0 (to retain the default keybindings in case
an user is used to them, while keeping number pad behaviour making sense,
similar to NetHack4+friends) was only partially implemented, for some reason.
This adds the rest of the keys, meaning that this means of key interpretation
should be more realible. KEY_A2/B1/B3/C2 are not standard keys in the Curses
documentation, and is thus behind an ifdef -- but PDCurses, amongst other
implementations, makes use of them.

As a side effect, Home/End/PgUp/PgDn are now interpreted as diagonal movement,
since some terminals interpret number_pad keys that way. I do not consider this
a problem since they went unused in normal gameplay anyway (This does not
interfere with menus or similar).