The constructors assert non null parameters.
__attribute__((nonnull)) for the declarations.
Merge pull request #48 from robrix/non-null-closure-property

Non null closure property
Check pointer equality before -isEqual:.

Avoids infinite loops on nil returns.
Delays terminate unbounded recursion.
Delay combinators terminate unbounded recursion.
Unused param style.
Merge branch 'master' into lexer

Conflicts:
	Hammer/HMRParserCombinator.m