totempg.h: change type of totempg_group.group_len from int to size_t

• include/corosync/totem/totempg.h (struct totempg_group) [group_len]:

Change member type from int to size_t.

git-svn-id: http://svn.fedorahosted.org/svn/corosync/trunk@2036 fd59a12c-fef9-0310-b244-a6a79926bd2f