Fix bug in ctable hash-to-index mapping
Fix bug in ctable hash-to-index mapping

Before, we would sometimes map a hash beyond the size of a table.  It
didn't usually matter before as resizing always visited 2*size.  Now
that resize precisely visits only the active entries -- those within
[0,size+max_displacement) -- now we see this bug.  Caught by the cltable
test suite, yay!

alexandergall/snabbswitch,Igalia/snabb,dpino/snabb,snabbco/snabb,SnabbCo/snabbswitch,snabbco/snabb,snabbco/snabb,dpino/snabbswitch,eugeneia/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,Igalia/snabbswitch,snabbco/snabb,eugeneia/snabbswitch,snabbco/snabb,alexandergall/snabbswitch,eugeneia/snabb,Igalia/snabbswitch,dpino/snabbswitch,eugeneia/snabb,heryii/snabb,eugeneia/snabb,eugeneia/snabbswitch,alexandergall/snabbswitch,Igalia/snabbswitch,eugeneia/snabb,alexandergall/snabbswitch,Igalia/snabb,eugeneia/snabb,Igalia/snabbswitch,Igalia/snabb,dpino/snabb,Igalia/snabbswitch,eugeneia/snabb,Igalia/snabb,alexandergall/snabbswitch,dpino/snabb,heryii/snabb,alexandergall/snabbswitch,Igalia/snabb,alexandergall/snabbswitch,heryii/snabb,Igalia/snabb,eugeneia/snabb,dpino/snabb,Igalia/snabb,heryii/snabb,snabbco/snabb,heryii/snabb,snabbco/snabb,heryii/snabb,dpino/snabb,dpino/snabbswitch,dpino/snabbswitch,dpino/snabb,SnabbCo/snabbswitch,eugeneia/snabb,Igalia/snabb,SnabbCo/snabbswitch,dpino/snabb,SnabbCo/snabbswitch,eugeneia/snabbswitch