FFL: Make tcp_ts_getticks() return uint32_t instead of u_int

[jtl]

Summary

Make tcp_ts_getticks() return uint32_t instead of u_int. While this isn't a "long", it is still an integer of unspecified size. In this case, we always want a 32-bit integer. (Granted, if an int is no longer 32 bits, there is much more code we should review.)

[jtl]

Committed in rS306769.