pppd: Widen types in ipcp_reqci

pppd: Widen types in ipcp_reqci

The reason is to avoid a theoretically possible overflow of cilen.
Using u_int32_t rather than u_short probably generates better code
on many machines anyway.  Also change l from int to unsigned so as
to avoid any possibility of integer overflow.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>