$NetBSD$

Install man-pages to proper directory.

--- doc/CMakeLists.txt.orig	2015-08-03 08:55:54.000000000 +0000
+++ doc/CMakeLists.txt
@@ -101,6 +101,7 @@ endif (XMLMANTOHTML_EXECUTABLE)
 
 ## Install
 
-install (FILES gsad.8
-  DESTINATION ${DATADIR}/man/man8 )
+include(GNUInstallDirs)
 
+install (FILES gsad.8
+  DESTINATION ${CMAKE_INSTALL_MANDIR}/man8 )