Rewrite memory block allocator.
Rewrite memory block allocator.

Use a mix of linear probing and pseudo-random probing.
Workaround for 1GB MAP_32BIT limit on Linux/x64. Now 2GB with !LJ_GC64.
Enforce 128TB LJ_GC64 limit for > 47 bit memory layouts (ARM64).

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