Merge master to features/ioperation

Merge remote-tracking branch 'upstream/master' into merges/master-to-features/ioperation-20170816-070014

Merge master to features/ioperation

Merge dev15.4.x to master

Use default tuple fields in conversion since fields from inferred names are marked not usable in C#7

Do a better job with leading trivia on types when moving types to a new file.

Adds feature that helps convert keywords and symbols in doc comments to the appropriate tags.

Refactored ILambdaExpression to IAnonymousFunctionExpression, Signatu…

Rename ILockStatement.LockedObject to Expression.

* dotnet/features/ioperation:
  Fixed unintentional capitalization change.
  Refactors INullCoalescingExpression to ICoalesce expression, and properties to sensible names.

Improve find-refs behavior when the user invokes it with a symbol selected

Fix regression in VB attribute classification.

In the introduction of the new 'this' optimization routine,
one of the things which was changed was to treat 'this' more
like a formal parameter of the method, as opposed to a variable
living in an implicit, higher scope. This has some advantages
in simplicity for analysis, but created a problem when it came
to proxies. The current analysis builds the proxy list by walking
the tree and finding all captured variables and adding them
to the proxy dictionary keyed by the original variable symbol.
For instance, if a local variable is captured to a field, during
rewriting it will be added to the proxy list as (original symbol,
hoisted field). Since most symbols are only ever captured to a
single replacement field, this usually works fine -- all proxies
can exist side-by-side in the proxy list since there is no intersection.

However, this is not true for captured environment pointers. When
a new environment is introduced, a local will be created to point
to that environment. That local may itself be captured by nested
variables, creating a linked list from nested scopes to parent scope.
Most notably, *multiple* nested environments may capture the *same*
environment pointer in *different* hoisted fields. This means that
the proxies dictionary cannot hold all mappings at once, since the
mapping for a given captured environment pointer will depend on the
current scope.

The current code actually accounts for this already by adding a
captured environment pointer to the proxy list on a nested scope's
introduction, and removing it upon leaving that scope.

By changing 'this' to be treated like a formal parameter, I
circumvented this logic, introducing a bug. When two scopes tried
to capture the 'this' pointer, the compiler crashed due to trying
to add two mappings to the same key.

This change fixes this problem by treating the 'this' parameter
like an environment pointer for the purposes of capturing and
hoisting. It's possible that we want to treat it like a formal
parameter, but if so it's probably better to treat all captured
environment pointers the same way and introduce a scope-aware
notion of proxies, rather than having a global dictionary.

Fixes #21506

Refactor comments in local function binder

Refactors INullCoalescingExpression to ICoalesce expression, and prop…

Move to GitLink 3.0.0

Merge remote-tracking branch 'upstream/master' into merges/master-to-features/ioperation-20170815-070014

are marked not usable in C#7

Reference the correct cibuild script