Target a minimal terminfo library rather than necessarily a full curses
library for color support detection. This still will use a curses
library if that is all we have available on the system. This change
tries to use a smaller subset of the curses library, specifically the
subset that is on some systems split off into a separate library. For
example, if you install ncurses configured --with-tinfo, a 'libtinfo' is
install that provides just the terminfo querying functionality. That
library is now used instead of curses when it is available.

This happens to fix a build error on systems with that library because
when we tried to link ncurses into the binary, we didn't pull tinfo in
as well. =]

It should also provide an easy path for supporting the NetBSD
libterminfo library, but as I don't have access to a NetBSD system I'm
leaving adding that support to those folks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188160 91177308-0d34-0410-b5e6-96231b3b80d8