MFC 254699,255030:
Use tvtohz() to convert a socket buffer timeout to a tick value rather
than using a home-rolled version.  The home-rolled version could result
in shorter-than-requested sleeps.

PR:		kern/181416
MFC 255248:
Use an unsigned long when indexing into mfchashtbl[] and mf6ctable[].  This
matches the types used when computing hash indices and the type of the
maximum size of mfchashtbl[].

PR:		kern/181821