Fixed crash on iOS 4 / Xcode 4.4+

Xcode >= 4.4 executes the +load method before linking libarclite.
The obvious fix is to do the intialisation in +initialize instead
of +load.

See http://stackoverflow.com/a/12528882/699208

Xcode <= 4.3:

LINKING libarclite_xxx.a
class's +load
class category's +load
int main()
class's +initialize

Xcode >= 4.4:

class's +load
LINKING libarclite_xxx.a
class category's +load
int main()
class's +initialize
Merge pull request #1 from raumfeld/master

Fix for a crash on iOS 4 / Xcode 4.4+