[clang] Add test for CWG1606 (#87274)

https://cplusplus.github.io/CWG/issues/1606.html

Author: NekoCdr

clang/test/CXX/drs/dr16xx.cpp

@@ -35,6 +35,17 @@ void g() {
 }
 } // namespace dr1601
 
+namespace dr1606 { // dr1606: 3.1
+#if __cplusplus >= 201103L
+  std::size_t test() {
+    int i = 1;
+    int j = 1;
+    auto f = [=]{ return i + j; };
+    return sizeof(f);
+  }
+#endif
+} // namespace dr1606
+
 namespace dr1611 { // dr1611: dup 1658
   struct A { A(int); };
   struct B : virtual A { virtual void f() = 0; };

clang/www/cxx_dr_status.html

@@ -9444,7 +9444,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/1606.html">1606</a></td>
     <td>NAD</td>
     <td><TT>sizeof</TT> closure class</td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 3.1</td>
   </tr>
   <tr id="1607">
     <td><a href="https://cplusplus.github.io/CWG/issues/1607.html">1607</a></td>