Add an overload to DocumentOptionSet.WithChangedOption

This adds a convenience overload where WithChangedOption can be more
easily used with a PerLanguageOption, but also returns a strongly
typed DocumentOptionSet so you don't lose the distinction.

src/Workspaces/Core/Portable/Options/DocumentOptionSet.cs

@@ -35,6 +35,14 @@ public override OptionSet WithChangedOption(OptionKey optionAndLanguage, object
             return new DocumentOptionSet(_backingOptionSet.WithChangedOption(optionAndLanguage, value), _language);
         }
 
+        /// <summary>
+        /// Creates a new <see cref="DocumentOptionSet" /> that contains the changed value.
+        /// </summary>
+        public DocumentOptionSet WithChangedOption<T>(PerLanguageOption<T> option, T value)
+        {
+            return (DocumentOptionSet)WithChangedOption(option, _language, value);
+        }
+
         internal override IEnumerable<OptionKey> GetChangedOptions(OptionSet optionSet)
         {
             return _backingOptionSet.GetChangedOptions(optionSet);

src/Workspaces/Core/Portable/PublicAPI.Unshipped.txt

 *REMOVED*Microsoft.CodeAnalysis.TextDocument.Project.set -> void
 *REMOVED*Microsoft.CodeAnalysis.TextDocument.TextDocument() -> void
+Microsoft.CodeAnalysis.Options.DocumentOptionSet.WithChangedOption<T>(Microsoft.CodeAnalysis.Options.PerLanguageOption<T> option, T value) -> Microsoft.CodeAnalysis.Options.DocumentOptionSet
 static Microsoft.CodeAnalysis.Formatting.Formatter.OrganizeImportsAsync(Microsoft.CodeAnalysis.Document document, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.CodeAnalysis.Document>
 static Microsoft.CodeAnalysis.Simplification.Simplifier.AddImportsAnnotation.get -> Microsoft.CodeAnalysis.SyntaxAnnotation