Modernize Xcode projects.

Set deployment to 10.7, remove SDK and ARCH settings (use Xcode 5
defaults), upgrade file format. Add workspace.
Convert to ARC.
Fix hashing to include full input string.

Original code omitted the last character thanks to misuse of strlen().
Notice that fixing this breaks compatibility with keys generated by the
original code.

See issue dchest/ellipticlicense#1.