Added missing cmake module.

CleanDirectoryList.cmake

+# - Removes duplicate entries and non-directories from a provided list
+#
+#  clean_directory_list(<listvar> [<additional list items>...])
+#
+# Requires CMake 2.6 or newer (uses the 'function' command)
+#
+# Original Author:
+# 2009-2010 Ryan Pavlik <rpavlik@iastate.edu> <abiryan@ryand.net>
+# http://academic.cleardefinition.com
+# Iowa State University HCI Graduate Program/VRAC
+#
+# Copyright Iowa State University 2009-2010.
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+
+if(__clean_directory_list)
+	return()
+endif()
+set(__clean_directory_list YES)
+
+function(clean_directory_list _var)
+	# combine variable's current value with additional list items
+	set(_in ${${_var}} ${ARGN})
+
+	if(_in)
+		# Initial list cleaning
+		list(REMOVE_DUPLICATES _in)
+
+		# Grab the absolute path of each actual directory
+		set(_out)
+		foreach(_dir ${_in})
+			if(IS_DIRECTORY "${_dir}")
+				get_filename_component(_dir "${_dir}" ABSOLUTE)
+				file(TO_CMAKE_PATH "${_dir}" _dir)
+				list(APPEND _out "${_dir}")
+			endif()
+		endforeach()
+
+		if(_out)
+			# Clean up the output list now
+			list(REMOVE_DUPLICATES _out)
+		endif()
+
+		# return _out
+		set(${_var} "${_out}" PARENT_SCOPE)
+	endif()
+endfunction()