bug#28893: emacs-26.0.90 minor build issue on OpenIndiana

[Nelson H. F. Beebe]

Paul Eggert proposes a small patch to the emacs-26.0.90 configure
script to deal with the build problem that I reported for OpenIndiana.

I've just done a fresh build on that system, and Paul's patch solves
the problem:

        diff configure.~1~ configure
        17027c17027
        <   for tputs_library in '' tinfo ncurses terminfo termcap curses; do
        ---
        >   for tputs_library in '' tinfo ncurses terminfo curses termcap; do

The build procedure went like this:

        set path= ( /bin /usr/bin /sbin /usr/sbin )

        env CONFIG_SITE= ./configure --prefix=$L --with-pop \
                --with-gnutls=no --with-gif=no && \
                gmake all check

        ... long output omitted...

        % ./src/emacs --version | head -1
        GNU Emacs 26.0.90

I suggest, however, that configure.ac acquire some explanatory
comments to document why -lcurses should be searched before -ltermcap
on OpenIndiana.

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