cmake: GNUInstallDirs for Debian compatibility
On Debian, the packaging helpers and infrastructure rely on cmake
projects including this CMake module -- otherwise various features such
as cross-compiling won't work correctly.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d295531..da1efbb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,8 @@
cmake_minimum_required(VERSION 2.8.9)
project(libyang C)
+include(GNUInstallDirs)
+
set(LIBYANG_DESCRIPTION "libyang is YANG data modelling language parser and toolkit written (and providing API) in C.")
# set version