cfengine_stdlib.cf now lives in "libraries"

Fixes #2724
(cherry picked from commit c7189f3f041b6ea14b0258f65b32ad43b4359dba)
Revert "Ensure scope 'this' is properly restored, add unit test."

This reverts commit f59e2c826237e1651f102e32200c84cdbf414e4d.

Only reverted in 3.5.x to proceed with performance testing
Merge remote-tracking branch 'upstream/3.5.x' into 3.5_surfsara