Update DLR (#752)

* Update DLR

* Fix test_cgcheck

Author: slozier

Src/DLR

@@ -268,7 +268,7 @@ public static void setdefaultencoding(CodeContext context, object name) {
                 throw PythonOps.LookupError("'{0}' does not match any available encodings", strName);
             }
 
-            pc.DefaultEncoding = enc;
+            pc.SetDefaultEncoding(enc);
         }
 
 #if PROFILE_SUPPORT

Src/IronPython/Modules/sys.cs

@@ -2093,7 +2093,7 @@ private static List SplitInternal(string self, char[] seps, int maxsplit) {
                 //  If the optional second argument sep is absent or None, the words are separated 
                 //  by arbitrary strings of whitespace characters (space, tab, newline, return, formfeed);
 
-                r = StringUtils.Split(self, seps, (maxsplit < 0) ? Int32.MaxValue : maxsplit + 1,
+                r = self.Split(seps, (maxsplit < 0) ? Int32.MaxValue : maxsplit + 1,
                     (seps == null) ? StringSplitOptions.RemoveEmptyEntries : StringSplitOptions.None);
 
                 List ret = PythonOps.MakeEmptyList(r.Length);

Src/IronPython/Runtime/Operations/StringOps.cs

@@ -1781,9 +1781,10 @@ public override void GetExceptionMessage(Exception exception, out string message
         /// <summary>
         /// Gets or sets the default encoding for this system state / engine.
         /// </summary>
-        public Encoding DefaultEncoding {
-            get { return _defaultEncoding; }
-            set { _defaultEncoding = value; }
+        public override Encoding DefaultEncoding => _defaultEncoding;
+
+        public void SetDefaultEncoding(Encoding encoding) {
+            _defaultEncoding = encoding;
         }
 
         public string GetDefaultEncodingName() {

Src/IronPython/Runtime/PythonContext.cs

@@ -90,11 +90,11 @@ def write_accessor(self, cw, transparent):
 
     def write_accessor_propertyinfo(self, cw):
         if self.emitAccessors == True :
-            cw.write('case VarEnum.VT_%s: return typeof(Variant).GetProperty("%s");' % (self.variantType, self.accessorName))
+            cw.write('case VarEnum.VT_%s: return typeof(Variant).GetProperty(nameof(Variant.%s));' % (self.variantType, self.accessorName))
 
     def write_byref_setters(self, cw):
         if self.emitAccessors == True :
-            cw.write('case VarEnum.VT_%s: return typeof(Variant).GetMethod("SetAsByref%s");' % (self.variantType, self.name))
+            cw.write('case VarEnum.VT_%s: return typeof(Variant).GetMethod(nameof(Variant.SetAsByref%s));' % (self.variantType, self.name))
 
     def write_ComToManagedPrimitiveTypes(self, cw):
         wrapper_types = ["CY", "DISPATCH", "UNKNOWN", "ERROR"]