poco: revert CMakeLists.txt changes for update
Squashed 'poco/' changes from 23760af..a64ebba


git-subtree-dir: poco
git-subtree-split: a64ebba3ee9972ad61d822403a62ea40396474a8
Merge commit 'e6c6b5ade09684562220e8128d11a1831781327c'
pothos: make use of poco ENABLE_* options