Confusion about NCURSES_PAIRS_T

[Chih-Hsuan Yen]

Hi NCurses experts,

Currently (v6_1_20190413) NCURSES_PAIRS_T is defined as `short`, and
in function `pair_content()`, the first argument `pair` accepts
1~COLOR_PAIRS-1, which is 1~65535 in some terminal types (e.g.,
xterm-256color, screen-256color). Does that mean NCURSES_PAIRS_T
should be a type with a larger range?

Noticing this when debugging https://bugs.python.org/issue36630.

Thanks,

Chih-Hsuan Yen