Allocate aligned pages in mem pool fuzzer
Allocate aligned pages in mem pool fuzzer

Otherwise the alignment tests can fail. OSS-Fuzz 12412

And also free the pages on exit otherwise OSS-Fuzz detects it
as a leak. OSS-Fuzz 12413

randombit/botan,randombit/botan,randombit/botan,webmaster128/botan,webmaster128/botan,webmaster128/botan,randombit/botan,webmaster128/botan,webmaster128/botan,randombit/botan