Remove never-implemented flag --indy. Fixes #2231.
[Truffle] Added a partial stub for Hash#default.
[Truffle] Implemented NilClass#to_h.
[Truffle] Add a script to check methods parity with MRI.
[Truffle] Use a BooleanCastNode instead of CoreLibrary.isTruthy().
[Truffle] Use @CreateCast instead of CoreLibrary.isTruthy().
[Truffle] De-duplicate guard and name it appropriately.
[Truffle] No need for a Bignum specialization anymore.
Update RubySpec from rubyspec/rubyspec @ 39701ac6.
[Truffle] Update tags for the changed specs.
[Truffle] Tags for temporarily failing Float specs.
Update tags for the changed specs.
Update list of slow language specs.
[Truffle] Add unary and binary core method nodes for expressivity.

* This is an experiment, it might prove difficult to handle some cases of ArgumentError, etc.
[Truffle] Add missed files to last commit.
[Truffle] Fix compilation.
Clean up block cloning for instance_eval and friends.

Conflicts:
	core/src/main/java/org/jruby/RubyBasicObject.java
	core/src/main/java/org/jruby/RubySymbol.java
Fully clone block + frame for instance_eval forms.

Fixes #1768 and #2060.
fix File.readable? when native is disabled

this readable? method now follows the same pattern as writable?, file?,
directory? and exists? and uses the respective FileResource directly.

fixes #2040 and #1983

Sponsored by Lookout Inc.
Merge remote-tracking branch 'origin/jruby-1_7'

Conflicts:
	core/src/main/java/org/jruby/RubyBasicObject.java
	core/src/main/java/org/jruby/RubySymbol.java
	core/src/main/java/org/jruby/runtime/Block.java
	core/src/main/java/org/jruby/runtime/BlockBody.java
	core/src/main/java/org/jruby/runtime/CompiledSharedScopeBlock.java
	core/src/main/java/org/jruby/runtime/SharedScopeBlock.java