Allow checking for exception equality and string comparisons.

I noticed this due to t/version_tag.t failing and blowing up.
is($@,"","chown wasn't supported in 2.13");
overload in 5.10 resets fallback each time its called.

Best to only call overload once.
Fix weird error during global destruction

(in cleanup) Can't use an undefined value as an ARRAY reference at
.../autodie/Scope/GuardStack.pm line 48 during global destruction.
Merge pull request #58 from maxmind/fix-global-destruction-weirdness

Fix weird error during global destruction
Merge pull request #57 from schwern/bug/exceptions-overload-fallback

Allow checking for exception equality and string comparisons.
RT#100688: Clean up tempfiles created in truncate.t

Signed-off-by: Niels Thykier <niels@thykier.net>