Added spec for -> {} in BasicObject class.
Added failing spec on splat assignment with many post-splat variables.
Added spec on super with a chain of anonymous modules.
Removed not_compliant_on :rubinius guards for language/variable specs.
Added method definition and parameter specs.
Added multiple assignment specs.
Updated lambda specs per Rubinius

This commit had to be imported manually as I couldn't get `git am` to work.
Apparently both Rubinius and rubyspec made various incompatible changes to the
same file.

The original Git commit in Rubinius is 65295a8b563fcd54f74e4663c1b88120367daf44.
Added specs for **obj in Hash literals.
More masgn spec improvements.
A few more masgn specs.
Added specs for calling #to_a on splatted arguments.
More method language specs.
Added attribute assignment specs.
Added specs for break in opasgn value.
Check return value of a, b, c = 1.
Check return value of a, (b, c) = 1, x.
Added specs for %i, %I.
Rewrote language/numbers specs.
Added block destructuring specs.
Added more splat assignment specs.

Adapted specs from https://github.com/rubyspec/rubyspec/pull/278.