Renamed String#from_cstr to String#new
Make "foo[:bar] ||= 1" be the same as "foo[:bar]? || (foo[:bar] = 1" and removed Hash#fetch_or_assign
Added the macros "getter! foo" and "property! foo" that define methods "foo" and "foo?": "foo" raises if @foo is nil, while "foo?" can be nil. Removed "not_nil!" checks from most places.
Bootstrap: allocate union pointer before returning from call