Adding Test.pm with workaround for Perl abs2rel bug

Adding Test.pm with workaround for Perl abs2rel bug

If SRCTOP != BLDTOP, and SRCTOP is given in relative form, e.g.
"./config ../openssl", then a bug in Perl's abs2rel may trigger that directory-
rewriting in __cwd results in wrong entries in %directories under certain
circumstances, e.g. when a test executes run(app(["openssl"]) after indir.

There should not be any need to go to a higher directory from BLDDIR or SRCDIR,
so it should be OK to use them in their absolute form, also resolving all
possible symlinks, right from the start.

Following the File::Spec::Functions bug description (reported to perl.org):

When abs2rel gets a path argument with ..s that are crossing over the ..s
trailing the base argument, the result is wrong.

Example
PATH: /home/goal/test/..
BASE: /home/goal/test/../../base
Good result: ../goal
Bad  result: ../..

Bug verified with File::Spec versions
- 3.6301
- 3.74 (latest)

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7031)