Freeze should return self.
Implement a naive upcase and downcase.
Really dumb implementation of String#unpack.
Implement defined?(@ivar)
Implement end_with?
Hash tuples in a way that actually works.
Improved Array#[]=
Fix Array#[](a,b) and StaticTuple#subary indexing.
Add Array#index.
Add Enumerable #min #max #one? #none? #count
Add Fixnum#chr
Add Object#tap
Add String#*
Add post-splat arguments to splat.

Specifically to fix 'regression' in rubyspec for 'a[*blah] = 1'
Merge branch 'parser-sprint'

This brings things to the level that
https://github.com/whitequark/parser can parse at least small amounts of
ruby code. It's mostly just small tweaks here and there to bring
incomplete behaviours closer to correctness.