Fix build warnings not reported by the Visual Studio 2015 compiler

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers/DocumentationRules/ElementDocumentationSummaryBase.cs

@@ -18,7 +18,6 @@ namespace StyleCop.Analyzers.DocumentationRules
     /// </summary>
     internal abstract class ElementDocumentationSummaryBase : DiagnosticAnalyzer
     {
-        private readonly Action<CompilationStartAnalysisContext> compilationStartAction;
         private readonly Action<SyntaxNodeAnalysisContext, StyleCopSettings> typeDeclarationAction;
         private readonly Action<SyntaxNodeAnalysisContext, StyleCopSettings> methodDeclarationAction;
         private readonly Action<SyntaxNodeAnalysisContext, StyleCopSettings> constructorDeclarationAction;

StyleCop.Analyzers/StyleCop.Analyzers/DocumentationRules/PartialElementDocumentationSummaryBase.cs

@@ -23,7 +23,6 @@ internal abstract class PartialElementDocumentationSummaryBase : DiagnosticAnaly
     {
         private static readonly XElement EmptyElement = new XElement("empty");
 
-        private readonly Action<CompilationStartAnalysisContext> compilationStartAction;
         private readonly Action<SyntaxNodeAnalysisContext, StyleCopSettings> typeDeclarationAction;
         private readonly Action<SyntaxNodeAnalysisContext, StyleCopSettings> methodDeclarationAction;