Revert "crypto: use better memory BIO implementation"

This change shouldn't have landed in the stable branch. It's a feature,
not a bug fix.

This reverts commit 58f93ffc4a23aa7240808288acf8cf9f3022abea.
This reverts commit 8c8ebe49b62c47b0ac87d697d0bc3515604667c3.
This reverts commit ba0f7b8066cb4dc8cb3cd4931e52aa94af40a709.
This reverts commit 21f3c5c3670861436392f30da2033cccbc137309.