OSX compatibility for source code.

This commit makes piwiktracker buildable (and working) under OS X. The library, compiled with those changes, works on both iOS and OS X.
Changes are:
Headers needed for OS X
A trick to avoid redefinition of DLog (I already have it defined in my projects). :)
Modification on calls to accommodate the differences between UIKit and AppKit.
Some string-format modification accomodating differences in size between variables between OS X and iOS (mostly 32- vs. 64-bitness issues).
The OS X version can be compiled 64-bit only and it's tested only on 10.7+.