ECMA 402 v2 made Intl constructors more strict in terms of how they would
initialize objects, refusing to initialize objects which have already
been constructed. However, when Chrome tried to ship these semantics,
we ran into web compatibility issues.

This patch tries to square the circle and implement the simpler v2 object
semantics while including a compatibility workaround to allow objects to
sort of be initialized later, storing the real underlying Intl object
in a symbol-named property.

The new semantics are described in this PR against the ECMA 402 spec:
https://github.com/tc39/ecma402/pull/84

BUG=v8:4360, v8:4870
LOG=Y

Review-Url: https://codereview.chromium.org/2582993002
Cr-Commit-Position: refs/heads/master@{#41943}

Spec discussion:  https://github.com/tc39/ecma402/issues/30

It's in stage 4 and Firefox has already implemented it.

For now, it's added to HARMONY_IN_PROGRESS bucket behind
'--datetime-format-to-parts' flag.

BUG=v8:5244
TEST=intl/date-format/date-format-to-parts.js
TEST=test262/intl402/DateTimeFormat/prototype/formatToParts/*

Review-Url: https://codereview.chromium.org/2273953003
Cr-Commit-Position: refs/heads/master@{#39225}

Nothing too important, but it helps localizing the cause of an error
much faster.
By the way, I also changed the output for assertThrows and
assertDoesNotThrow a bit.
All new arguments are optional, so everything is backwards compatible.

R=jfb@chromium.org, titzer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1866693002

Cr-Commit-Position: refs/heads/master@{#35322}

BUG=v8:2745
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/18687003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15584 ce2b1a6d-e550-0410-aec6-3dcde31c8c00