Add and fix sharing specs for Range#{cover?,include?,member?,===}
Fix Range#{include?,member?} for X19

It should basically depend element.succ from X19.
And old behavior is keeping by Range#cover?.

Example
-------

    ('a'..'c').include? 'bc'

Results
-------

* MRI 1.8.7    #=> true
* MRI 1.9.3    #=> false
* Rubinius X18 #=> true
* Rubinius X19 #=> true  #Fix here
Add the 'commands' command to Rubinius' debugger

The 'commands' command allows the user to specify a list of debugging
statements that are automatically executed whenever a certain breakpoint is
triggered.

This command takes inspiration from GDB's 'commands' one.
Add specs on Numeric#step called as ±inf.step(±inf, ±step).
Numeric#step: stop if err is not finite.
Merge pull request #2434 from heftig/master

 Allow linking against a shared libLLVM
Merge pull request #2426 from razielgn/feature-numeric-step-infinity-combinations

Numeric#step called as ±inf.step(±inf, ±step)
Merge pull request #2416 from kachick/fix-range-include-x19

Range#{include?,member?} should basically depend element.succ from X19
Remove unused method from LLVM state
Don't do conditional check for clearing values when setting encoding

This makes sure we don't have any uninitialized reads and comparisons
against those.
Add specs for Kernel#extend
Fix Kernel#extend when no arguments given
Add spec for yaml dumping StringIO
Fix YAML dumping for StringIO

Fixes #2425
Improve debug output for JIT inlining

This also prints all types for all other cases in the inlining when we
don't inline or inline a primitive.
Add a spec for Enumerable#chunk when given a mutable initial_state
Fix Enumerable#chunk when given a mutable initial_state

* Duplicate only the every first iteration. Not every iterations.
* Use #dup instead of #clone to duplicate the object.
Turn callsites into monomorphic sites

This makes sure these call sites don't go polymorphic when using
different String subtypes. This happens quite a bit in Rails, where
different types end up being used.

By calling .equal? on undefined, we make sure we check against the same
object all the time, turning the call site monomorphic and better
inlineable.
Use binary encoding directly instead if finding it with the index
Merge pull request #2440 from kachick/fix-enum-chunk-with_init

Fix Enumerable#chunk when given a mutable initial_state