make USE_GNU_DEMANGLE cmake variable OFF on linux

- fix setting the default USE_GNU_DEMANGLE setting to OFF on linux and freebsd
  as libiberty is now required.
- move include(shared) before include(LibIberty) so PLATFORM is defined

CMakeLists.txt

@@ -29,9 +29,9 @@ find_package(Threads)
 include(Boost)
 include(ThreadingBuildingBlocks)
 include(ElfUtils)
-include(LibIberty)
 
 include(shared)
+include(LibIberty)
 
 if(USE_OpenMP)
   find_package(OpenMP REQUIRED)

cmake/LibIberty.cmake

@@ -34,6 +34,8 @@ endif()
 
 # Use the GNU C++ name demangler; if yes, this disables using LibIberty
 if (PLATFORM MATCHES linux OR PLATFORM MATCHES freebsd)
+  set(USE_GNU_DEMANGLER OFF CACHE BOOL "Use the GNU C++ name demangler")
+else()
   set(USE_GNU_DEMANGLER ON CACHE BOOL "Use the GNU C++ name demangler")
 endif()