Change type for constant expressions to Constant
Create better KeyError if hash key is missing
Add support for 1.9 named hash arguments in sprintf

We use the same parsing for 1.8 and 1.9 mode, just the regular
expression is different so the new 1.9 style is never matched by the 1.8
regexp. This makes for less duplicate code, while supporting both modes
properly.

Fixes #1627
Remove tags for passing sprintf specs
Update tags for 2.0 mode
Add specs for Regexp#match and String#match
Use character offsets for String#match and Regexp#match

Fixes #1965
Use call fallback when type bits check fail

When an object is inflated, the type bits check fails, so we have to
fallback to the helper function. In the future we should make it so that
type bits are in the object header, even for inflated objects.

Fixes #2205
Add specs for multibyte strings and String#(tr|tr_s)
Ensure String#(tr|tr_s) work properly with multibyte strings

Fixes #2157
Remove tags for passing specs
Setup thread name for agent thread
Remove unused Ruby Agent side

We don't have anything of this at the Ruby side atm, so removing it for
now. We should see how we want to handle this in the future and set it
up properly.

Fixes the hang mentioned in #2197
Compiled code only needs to be on stack if internalized

We only need to mark this as on stack when internalizing, since only
internalize could cause a lock and needs the compiled code object to be
updated.
Use a special update method for updating GC references in inline caches

Problem here was that using assign() also resets the hit counters,
leading to wrong heuristics on whether a method is called often or not.
In certain cases this could lead to hot methods not being inlined.
Cleanup duplicate rbx_get_ivar helper
Blog post: PDX Summit Recap.
Regen'd website.
Fix typo
Merge pull request #2218 from adzankich/io19_typo

Fix typo in io19.rb