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
Remove exports for symbols that are available for libc_nonshared

Apperently on RHEL / CentOS 5.9 this breaks the compile since these
symbols are exported there. Also checked against Ubuntu and the symbols
are available there too.

Fixes #2217
Return empty Hash if there are no coverage results.
Add a blog post for profiling JIT-ted code with OProfile