Link against Perl 5.12 on OS X 10.7-10.9, using the 10.8 SDK.

Previously, Pester on 10.6-10.8 linked against Perl 5.10.  On 10.6, Pester continues to use Perl 5.10.

This is necessary because 10.9 drops support for Perl 5.10 (and adds 5.16).

This change means Pester no longer compiles on (Mac) OS X 10.6 or 10.7, though it's trivial enough to edit/remove the ParseDate-10.7 target.  The Mac OS X 10.6 SDK doesn't work with Xcode 5 (even in 32-bit mode), though Pester should compile if you switch to the OS X 10.8 SDK. A future version will add Xcode 5 compatibility and move off the 10.6 SDK entirely.
Pester 1.1b17