[C11] Claim conformance to WG14 N1514

This paper made Annex G a normative, but conditionally supported,
annex. Clang does not implement Annex G, so we conform to this paper.

clang/test/C/C11/n1514.c

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -verify -std=c11 %s
+// expected-no-diagnostics
+
+/* WG14 N1514: Yes
+ * Conditional normative status for Annex G
+ */
+
+// We don't support Annex G (which introduces imaginary types), but support for
+// this annex is conditional in C11. So we can test for conformance to this
+// paper by ensuring we don't define the macro claiming we support Annex G.
+
+#ifdef __STDC_IEC_559_COMPLEX__
+#error "when did this happen??"
+#endif

clang/www/c_status.html

@@ -568,7 +568,7 @@ <h2 id="c11">C11 implementation status</h2>
     <tr>
       <td>Conditional normative status for Annex G</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1514.pdf">N1514</a></td>
-      <td class="unknown" align="center">Unknown</td>
+      <td class="full" align="center">Yes <a href="#annex-g">(1)</a></td>
     </tr>
     <tr>
       <td>Creation of complex value</td>
@@ -606,6 +606,9 @@ <h2 id="c11">C11 implementation status</h2>
       <td class="unknown" align="center">Unknown</td>
     </tr>
 </table>
+<span id="annex-g">(1): Clang does not implement Annex G, so our conditional support
+conforms by not defining the <code>__STDC_IEC_559_COMPLEX__</code> macro.
+</span>
 </details>
 
 <h2 id="c17">C17 implementation status</h2>