Make .pc files installation non-optional

[David Seifert]

Dear ncurses maintainers,
with the switch to ncurses 6.0, we have been experiencing a high number
of build failures involving ncurses in Gentoo. The main reason for this
is the assumption by upstream developers that -lncurses suffices for
linking (which is not true anymore). The proper fix for this situation
would be to use pkg-config. Alas, this is not a popular solution, as
.pc files cannot be relied upon, due to ncurses installing them only
when configured with --enable-pc-files. I would therefore like to
request that ncurses install the .pc files unconditionally (like pretty
much all other libraries), such that we can rely on them and do not
have to use broken hacks like AX_WITH_CURSES (which requires updating
anyhow). Do you consider this possible? It would solve a number of
problems going forward and reduce breakage should you decide to change
the linking flags.

Regards
David Seifert