Strip trailing options hash in Open3.popen3 and warn if non-empty.

Fixes #2298.
Don't acquire umask (mutexed) when we're not creating a file.
Use absolute path, not canonical, for LOADED_FEATURES.
Add regression spec for LOADED_FEATURES not expanding symlinks.
Remove pathname.rb from sync, since we have a custom version.
Sole remaining diff with MRI stdlib.
Update to RubyGems 2.4.5.
Update to latest 2.0 stdlib (p598, r48636).
Update patchlevel and revision for all modes.
Fixes #2172 on 1.9 and only for interpreted mode
JIT changes for Symbol encoding issue #2172.
Preserve incoming encoding in File.basename. Fixes #2259.
tests now passing from #2172 getting fixed
copy the old eventHooks list when adding a new eventHook

fixes #2296

Sponsored by Lookout Inc.
fix the osgi tests by improving the test whether posix uses native or not
Green CI without fixing underlying cause.  FORCE is broken in 1.8 mode
Fix 1.8 symbol compilation after encoding change. Fixes #2307.
Handle NCDFE for odd envs like GAE that throw it for Unsafe.

Fixes #2304.
Open3.capture* only exist on 1.9+.
[openssl] X509 cert extension authority key identifier finally matches MRI ...