Remove all checking for the various terminfo headers (term.h and

Remove all checking for the various terminfo headers (term.h and
curses.h). Finding these headers is next to impossible. For example, on
Debian systems libtinfo-dev provides the terminfo reading library we
want, but *not* term.h. For the header, you have to use libncurses-dev.
And libncursesw-dev provides a *different* term.h in a different
location!

These headers aren't worth it. We want two functions the signatures of
which are clearly spec'ed in sys-v and other documentation. Just declare
them ourselves and call them. This should fix some debian builders and
provide better support for "minimal" debian systems that do want color
autodetection.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188165 91177308-0d34-0410-b5e6-96231b3b80d8