[clang] [C99] Claim conformance for _Complex support (PR #88161)

[Joshua Cranmer via cfe-commits]

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@@ -373,6 +355,10 @@ <h2 id="c99">C99 implementation status</h2>
       <td class="full" align="center">Yes</td>
     </tr>
 </table>
+<span id="complex">(2): Clang supports <code>_Complex</code> type specifiers but
+does not support <code>_Imaginary</code> type specifiers. Support for
+<code>_Imaginary</code> is optional in C99 which is why Clang is fully conforming.
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jcranmer-intel wrote:

Maybe mention here something about not claiming Annex G conformance?

https://github.com/llvm/llvm-project/pull/88161