Fix default hash function bug in ctable
Fix default hash function bug in ctable

Zomg people!  I was hashing trash memory after the allocation, due to a
boneheaded confusion between zero-based and one-based indexes and
inclusive vs exclusive end bounds in FFI versus native Lua data.  The
tests did exercise this case but it happened not to matter.  FML.

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