windows.cfg: Add support for `__alignof()` (#2271)

Reference:
https://docs.microsoft.com/en-us/cpp/cpp/alignof-operator?view=vs-2019

cfg/windows.cfg

@@ -6338,6 +6338,15 @@ HFONT CreateFont(
       <not-bool/>
     </arg>
   </function>
+  <!-- __alignof Operator, declaration could look like this: size_t __alignof(type); -->
+  <!-- _alignof is a synonym -->
+  <function name="__alignof,_alignof">
+    <noreturn>false</noreturn>
+    <returnValue type="size_t"/>
+    <use-retval/>
+    <leak-ignore/>
+    <arg nr="1" direction="in"/>
+  </function>
   <podtype name="POINTER_SIGNED" sign="s"/>
   <podtype name="POINTER_UNSIGNED" sign="u"/>
   <podtype name="__time32_t" sign="s" size="4"/>

test/cfg/windows.cpp

@@ -192,6 +192,9 @@ void validCode()
 
     ::PostMessage(nullptr, WM_QUIT, 0, 0);
 
+    printf("%zu", __alignof(int));
+    printf("%zu", _alignof(double));
+
     // Valid Library usage, no leaks, valid arguments
     HINSTANCE hInstLib = LoadLibrary(L"My.dll");
     FreeLibrary(hInstLib);