gitignore: add gpioctl

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
Licenses: introduce SPDX Unique License Identifiers

Instead of including a big block with a license header in all files, just
use a single line reference to unique license identifiers as defined by
the Linux Foundation's SPDX project [1].

The complete list of unique license identifiers is available at [2].

[1] http://spdx.org/
[2] http://spdx.org/licenses/

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
pkgconfig: fix propagated include directory

Thanks to Fredrik Svensson for reporting and providing a patch
for this issue.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>