.gitignore: add cmake, build artifacts, and vim swap files
.gitignore: add cmake, build artifacts, and vim swap files

Newer versions of cmake seem to generate new build
artifacts.
This shows up at least with cmake version 3.7.2 (on Ubuntu 17.04).

Also, it should be a good idea to ignore generated libs
and .pc file.

Vim swap files are notorious for being added by accident.

Signed-off-by: Alexandru Ardelean <c8ec8d7216643db8a88f8dd26a8db4e136d951e0@analog.com>

analogdevicesinc/libad9361-iio,analogdevicesinc/libad9361-iio,analogdevicesinc/libad9361-iio,analogdevicesinc/libad9361-iio