Add specs for Hash#default_proc=
Fix Hash#default_proc= for frozen instance
Fix Hash#default_proc= for 2.0
Fix Hash.[] for 2.0

Named from Hash.new_from_literal.
Replace Hash by Type on load_order to privatize a class method in Hash
Merge pull request #2460 from kachick/2.0-hash

Hash.[], Hash#default_proc= for 2.0