Fix for gcc thanks to Ivano Ras

git-svn-id: http://svn.code.sf.net/p/ifcopenshell/svn/trunk@192 68180887-8925-40e4-aed3-789c086970ef
Improvements to Wavefront OBJ serialization, patch by Ivano Ras

git-svn-id: http://svn.code.sf.net/p/ifcopenshell/svn/trunk@193 68180887-8925-40e4-aed3-789c086970ef