merge opcua-cmake part1
Merge pull request #82 from mdcb-gmt/master

- use #pragma once for include
clean and fix cmake file. remove clang option, this should control using CXX variable
Merge branch 'master' of github.com:FreeOpcUa/freeopcua
Merge pull request #81 from oroulet/master

merge opcua-cmake
more fixes in cmake
valgrind check: do not read potentially deleted variables
Merge pull request #83 from oroulet/master

valgrind check: do not read potentially deleted variables