[C2y] Claim conformance to N3347

This paper made it a constraint violation to have a tentative
definition with internal linkage which is not completed by the end of
the translation unit.

This has been diagnosed as an error since at least Clang 3.0, so no
changes are needed.

Author: AaronBallman

clang/test/C/C2y/n3347.c

@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -verify -std=c2y -Wall -pedantic %s
+
+/* WG14 N3347: Yes
+ * Slay Some Earthly Demons IX
+ *
+ * Declarations of a tentative definition with internal linkage must be
+ * complete by the end of the translation unit.
+ */
+
+struct foo; // #foo
+static struct foo f1; /* expected-warning {{tentative definition of variable with internal linkage has incomplete non-array type 'struct foo'}}
+                         expected-error {{tentative definition has type 'struct foo' that is never completed}}
+                         expected-note@#foo 2 {{forward declaration of 'struct foo'}}
+                       */
+
+extern struct foo f2; // Ok, does not have internal linkage
+
+struct bar; // #bar
+static struct bar b; /* expected-warning {{tentative definition of variable with internal linkage has incomplete non-array type 'struct bar'}}
+                        expected-note@#bar {{forward declaration of 'struct bar'}}
+                      */
+struct bar { int x; };
+

clang/www/c_status.html

@@ -258,7 +258,7 @@ <h2 id="c2y">C2y implementation status</h2>
     <tr>
       <td>Slay Some Earthly Demons IX</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3347.pdf">N3347</a></td>
-      <td class="unknown" align="center">Unknown</td>
+      <td class="full" align="center">Yes</td>
 	</tr>
     <tr>
       <td>stdarg.h wording... v3</td>