travis-ci: install ncurses and cdk on macos
travis-ci: install ncurses and cdk on macos

use brew to install ncurses and cdk on macos, to see if we can build
iio-monitor in the examples dir, to compile test more things.

Signed-off-by: Robin Getz <c66e5a86ef9317cf35cecb2ed063996b2100ed4b@analog.com>

analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio,analogdevicesinc/libiio