Fix StackOverflow in NonAsciiRewriter

It is incorrect for the visitor to call the base visit method one a
literal node we don't rewrite. Doing so causes stack overflow due to
infinite recursion.

Author: ellismg

src/Microsoft.DotNet.CodeFormatting.Tests/Rules/NonAsciiCharactersAreEscapedInLiteralsRuleTests.cs

@@ -48,6 +48,21 @@ class Test
             Verify(text, expected);
         }
 
+        [Fact]
+        public void NonAsciiRewriterHandlesNonStringLiterals()
+        {
+            var text = @"
+using System;
+
+class Test
+{
+    public const int OkayInt = 12345;
+}
+";
+
+            Verify(text, text);
+        }
+
         internal override IFormattingRule GetFormattingRule()
         {
             return new Rules.NonAsciiChractersAreEscapedInLiterals();

src/Microsoft.DotNet.CodeFormatting/Rules/NonAsciiCharactersAreEscapedInLiteralsRule.cs

@@ -50,7 +50,7 @@ public override SyntaxNode VisitLiteralExpression(LiteralExpressionSyntax node)
                         return RewriteCharacterLiteralExpression(node);
                 }
 
-                return base.Visit(node);
+                return node;
             }
 
             private static SyntaxNode RewriteStringLiteralExpression(LiteralExpressionSyntax node)