Remove three unused fields in struct s_client.

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8517 4b0bc96b-bc66-0410-9d44-ebda105a78c1
oscam-client: Remove duplicated function.

check_client() and is_valid_client() are exactly the same.

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8518 4b0bc96b-bc66-0410-9d44-ebda105a78c1