Explicit visibility trivia handling

This change addresses how we handle trivia when inserting explicit
visibility on a member / type.  The previous code incorrectly used
the leading trivia of the node in question to position the first
visibility modifier.  That would end up combining trivia from say
before and after an attribute attached to the node which was
incorrect.  Now we grab the trivia from the node / type itself
and use that.

closes #86

Author: jaredpar

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

@@ -391,6 +391,162 @@ internal class C
                 Verify(text, expected, runFormatter: false);
             }
 
+            [Fact]
+            public void CommentAttributeAndType()
+            {
+                var text = @"
+// Hello
+[Attr]
+// World
+class C1 { }
+
+// Hello
+[Attr]
+// World
+partial class C2 { }";
+
+                var expected = @"
+// Hello
+[Attr]
+// World
+internal class C1 { }
+
+// Hello
+[Attr]
+// World
+internal partial class C2 { }";
+
+                Verify(text, expected);
+            }
+
+            [Fact]
+            public void CommentAttributeAndMethod()
+            {
+                var text = @"
+class C
+{
+    // Hello
+    [Attr]
+    // World
+    void M1() { }
+
+    // Hello
+    [Attr]
+    // World
+    static void M2() { }
+};";
+
+                var expected = @"
+internal class C
+{
+    // Hello
+    [Attr]
+    // World
+    private void M1() { }
+
+    // Hello
+    [Attr]
+    // World
+    private static void M2() { }
+};";
+
+                Verify(text, expected);
+
+            }
+
+            [Fact]
+            public void CommentAttributeAndProperty()
+            {
+                var text = @"
+class C
+{
+    // Hello
+    [Attr]
+    // World
+    int P1 { get { return 0; } }
+
+    // Hello
+    [Attr]
+    // World
+    static int P2 { get { return 0; } }
+};";
+
+                var expected = @"
+internal class C
+{
+    // Hello
+    [Attr]
+    // World
+    private int P1 { get { return 0; } }
+
+    // Hello
+    [Attr]
+    // World
+    private static int P2 { get { return 0; } }
+};";
+
+                Verify(text, expected);
+
+            }
+
+            [Fact]
+            public void CommentAttributeAndConstructor()
+            {
+                var text = @"
+class C
+{
+    // Hello
+    [Attr]
+    // World
+    C(int p1) { }
+
+    // Hello
+    [Attr]
+    // World
+    unsafe C(int p1, int p2) { }
+};";
+
+                var expected = @"
+internal class C
+{
+    // Hello
+    [Attr]
+    // World
+    private C(int p1) { }
+
+    // Hello
+    [Attr]
+    // World
+    private unsafe C(int p1, int p2) { }
+};";
+
+                Verify(text, expected);
+
+            }
+
+            public void CommentAttributeAndMultipleField()
+            {
+                var text = @"
+class C 
+{
+    // Hello
+    [Attr]
+    // World
+    int x, y;
+};";
+
+                var expected = @"
+internal class C 
+{
+    // Hello
+    [Attr]
+    // World
+    private int x, y;
+};";
+
+                Verify(text, expected);
+            }
+
             [Fact]
             public void Issue70()
             {