Revert changes made to Engine.pm in 1ef7eeb (5.90070)

Revert changes made to Engine.pm in 1ef7eeb (5.90070)

In 1ef7eeb ("removed old PSGI Engine backcompat ") some back compat code
was removed from lib/Catalyst/Engine.pm. But, this backcompat code is
apparently still needed and being used out in the wild.

This breaks the tests of at least:

 Catalyst-Plugin-Authentication-0.10023
 t/live_app_remote1.t

This commit restores the lines removed, going back to the state of the
last production release, 5.90065:

 git checkout 5.90065 -- lib/Catalyst/Engine.pm

Also re-applied change in 08680694151