Fix arguments of pf_purge_expired_{src_nodes,rules}()

Fix arguments of pf_purge_expired_{src_nodes,rules}()

Due to the missing "void", this

   extern void pf_purge_expired_src_nodes();

is no prototype but a declaration. It is enough to suppress the
'implicit declaration' warning but it does not allow the compiler to
check the arguments passed to the calls of the function.

Fix the prototypes and don't pass the waslocked argument anymore. It has
been removed a year ago.

ok sashan henning