Race condition in the rmtree and remove_tree functions allows attackers to set the mode on arbitrary files via vectors involving directory-permission loosening logic.
On 5.8.x, the installation would be shadowed by the core files, and thus not be visible. Makefile.PL tweaked appropriately to ensure that the installation overwrites the core files. Users on 5.6 and below need not upgrade, users on 5.8 should. Bug spotted by imacat (#30459).
Minor changes to the way POD tests are initialised.