api cleanup: replace BMO_vert_edge_flags_count() with more reusable function - BMO_iter_elem_count_flag().
closely matching existing BM_iter_elem_count_flag() function but checks tool-flags instead.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55623 954f8c5b-7b00-dc11-b283-0030488c597c