Moved GNU header define.
Merge pull request #17 from chead/feature/15_cleanup_gnu_define

Moved GNU header define.
Removed references to authentication type. Authentication is now only OOB.
Merge pull request #19 from chead/feature/18_remove_authentication_types

Removed references to authentication type. Authentication is now only OOB
Merge remote-tracking branch 'origin/develop' into feature/12_error_strings

Conflicts:
	src/twitter_authorization.h