Ensure that error codes being suppressed are always prefixed with 'CS'

Author: DustinCampbell

src/OmniSharp.MSBuild/MSBuildProjectSystem.cs

@@ -215,8 +215,8 @@ private static CSharpCompilationOptions CreateCompilationOptions(ProjectFileInfo
 
             var specificDiagnosticOptions = new Dictionary<string, ReportDiagnostic>(projectFileInfo.SuppressedDiagnosticIds.Count);
 
-            // Always suppress 1701 (Assuming assembly reference 'x' used by 'y' matches identity 'z'. you may need to supply runtime policy)
-            specificDiagnosticOptions.Add("1701", ReportDiagnostic.Suppress);
+            // Always suppress CS1701 (Assuming assembly reference 'x' used by 'y' matches identity 'z'. you may need to supply runtime policy)
+            specificDiagnosticOptions.Add("CS1701", ReportDiagnostic.Suppress);
 
             if (projectFileInfo.SuppressedDiagnosticIds.Any())
             {

src/OmniSharp.MSBuild/ProjectFile/PropertyConverter.cs

@@ -94,7 +94,7 @@ public static IList<string> ToSuppressDiagnostics(string propertyValue)
                 ushort number;
                 if (ushort.TryParse(id, NumberStyles.Integer, CultureInfo.InvariantCulture, out number))
                 {
-                    result.Add(id);
+                    result.Add("CS" + number.ToString("0000"));
                 }
             }