Reverting "gnu: ncurses: Build libtinfo."

This reverts commit 953c9fcf8c.  It turns
out that most packages (guile-ncurses, cursynth, aumix, util-linux,
etc.) expect libncurses to provide everything.  So they had to be
patched to add -ltinfow to their LDFLAGS, which is counterproductive.

Other recent distros take that approach---e.g.,
<https://bugs.launchpad.net/ubuntu/+source/ncurses/+bug/259139>.

gnu/packages/ncurses.scm

@@ -94,9 +94,6 @@
       `(#:configure-flags
         `("--with-shared" "--without-debug" "--enable-widec"
 
-          ;; Create a separate libtinfo.so, as many distributions do.
-          "--with-termlib"
-
           ;; By default headers land in an `ncursesw' subdir, which is not
           ;; what users expect.
           ,(string-append "--includedir=" (assoc-ref %outputs "out")