Added explicit conversion expression tests for C#.

Vb implicit conversions

Merge master to features/ioperation

* dotnet/features/ioperation: (60 commits)
  Fix unit test failures from merge conflict resolution
  removed double empty line
  remove duplicated test
  Fix build break in VB
  Address some more review feedback and fix one more break.
  Fix build break from merge conflict resolution
  added vb tests
  fixed failed tests
  added csharp unary operator expression test
  missed adding simple to one comment
  addressed PR feedback
  Add entries for dev15.3.x branch in readme.md
  Don't assume a document has SyntaxFactsService
  Skip CSharpInteractive.TypingHelpDirectiveWorks test
  Don't fetch every PR ref for every PR job
  create dump files when VS instance crashes or hangs (integration tests) (#20129)
  Clear completion pattern matcher caches on solution close (#20463)
  made all tests pass
  Address PR feedback from Chuck
  Cast the correct object to IVsBrowseObjectContext
  ...

Merge remote-tracking branch 'dotnet/features/ioperation' into merges/master-to-features/ioperation-20170705-070014

* dotnet/features/ioperation:
  Fix unit test failures from merge conflict resolution
  removed double empty line
  remove duplicated test
  Fix build break in VB
  Address some more review feedback and fix one more break.
  Fix build break from merge conflict resolution
  added vb tests
  fixed failed tests
  added csharp unary operator expression test
  Address PR feedback from Chuck
  Address some PR feedback from prior change
  Fix unit test failures
  Actually fix the build break from merge conflict resolution.
  Fix incorrectly resolved merge conflict
  Add IOperation support for anonymous object creation expressions.

Add IOperation support for anonymous object creation expressions.

Merge remote-tracking branch 'dotnet/master' into merges/master-to-features/ioperation-20170705-070014

* dotnet/master: (325 commits)
  Report when a `void` value is the subject of a pattern-match (#20578)
  Improve Extract Method exception message
  Refactor BuildNumberFiveDigitDateStamp expression to fix NuGet restore
  Disable test explorer by removing the xUnit Visual Studio runner
  Rename method.
  Cache previous results of NavigateTo so we can filter quickly as the user types.
  Classify discards as identifier (#20561)
  & is causing trouble in XML comments
  CR feedback of fixed statement
  Removed more dead build logic
  Fix IntelliSense in VSSDK projects that do not produce a VSIX
  Properly disable dependencies node
  Remove more dead code from our msbuild logic
  Remove ExeNonDeployment
  Clean up unit test MSBuild information
  Simplify code.
  Enable test.
  Add more information to test run to help track down failure.
  Work around uninstall issue with our VSIX
  Avoid costly check on every candidate we check against.
  ...

added unary operator expression tests

Exception workarounds

Eliminate a boxing allocation in DiagnosticIncrementalAnalyzer.InMemoryStorage

Fixes #20452

Get Live Unit Testing working with current Roslyn targets...

fix race on _storage field.

Improve Extract Method exception message

Disable test explorer by removing the xUnit Visual Studio runner

Related to https://devdiv.visualstudio.com/DevDiv/_workitems/edit/459425.

Extract Method maintains a table mapping various properties of a
variable (e.g. if it is captured, declared, assigned, etc.) to a "style"
controlling how that variable will look in the generated code. There
are 256 (2^8) possible combinations of these various properties, but the
table currently only maps 69 of them to a particular style. Presumably
we believe the unmapped combinations shouldn't/can't occur; however, we
have error data indicating otherwise.

This change updates the exception thrown when the table does not contain
a particular combination to include the properties. Since `Key.GetHashCode()`
already encodes the values into the hash code in a lossless way, we simply
reuse that.

Avoid costly check on every candidate we check against.

Cache previous results of NavigateTo so we can filter quickly as the user types.

Add more information to test run to help track down failure.