Merge in MemPools objectification.

Merge in MemPools objectification.

Patches applied:

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--base-0
   tag of robertc@squid-cache.org--squid/squid--HEAD--3.0--patch-369

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-1
   MemPools C++ rework.

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-2
   Tidying up.

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-3
   merge from HEAD

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-4
   merge from HEAD

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-5
   merge from HEAD

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-6
   fix up remaining splay tweaks for mempools, and update test suite

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-7
   Allow runtime pool type selection.

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-8
   MemProxyAllocator changes.

 * robertc@squid-cache.org--squid/squid--MemPools--3.0--patch-9
   merge latest head changes