client.h: Added check_version() prototype

Signed-off-by: ERIK ALEXANDRE PUCCI <eap08@c3sl.ufpr.br>
Acked-by: Bruno Ribas <ribas@c3sl.ufpr.br>
Acked-by: Josiney de Souza <josineys@c3sl.ufpr.br>
Signed-off-by: Danilo K. S. Yorinori <danilok@c3sl.ufpr.br>