login: Check default sizes of structs utmp, utmpx, lastlog

The default <utmp-size.h> is for ports with a 64-bit time_t.
Ports with a 32-bit time_t or with __WORDSIZE_TIME64_COMPAT32=1
need to override it.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>