bug#50444: Remove support for the curses library

[Stefan Kangas]

Severity: wishlist
X-Debbugs-CC: Paul Eggert <eggert@cs.ucla.edu>

Building with curses is, according to Paul Eggert:

    "Completely broken" in the sense it won't link and Emacs won't build,
    yes. (It will link in master, due to a patch I installed recently.)

    And yes, the original curses library has been obsolete for at least two
    decades.

See the discussion here:
https://lists.gnu.org/archive/html/emacs-devel/2021-01/msg00416.html

The conclusion from that thread AFAIU is that support for curses
should be removed.  (We should keep ncurses though.)