Variant.hpp: size_t include

ax3l · ax3l · commit 4af321bbfc36 · 2021-05-13T12:40:08.000-07:00
Fix the following error on macOS:
```
In file included from openPMD-api/include/openPMD/Iteration.hpp:24,
                 from openPMD-api/src/Iteration.cpp:21:
openPMD-api/include/openPMD/auxiliary/Variant.hpp:81:15: error: 'size_t' does not name a type
   81 |     constexpr size_t index() const noexcept
      |               ^~~~~~
openPMD-api/include/openPMD/auxiliary/Variant.hpp:1:1: note: 'size_t' is defined in header '&lt;cstddef&gt;'; did you forget to '#include &lt;cstddef&gt;'?
  +++ |+#include &lt;cstddef&gt;
```
diff --git a/include/openPMD/auxiliary/Variant.hpp b/include/openPMD/auxiliary/Variant.hpp
@@ -1,4 +1,4 @@
-/* Copyright 2017-2020 Fabian Koller
+/* Copyright 2017-2021 Fabian Koller, Axel Huebl
  *
  * This file is part of openPMD-api.
  *
@@ -22,6 +22,7 @@
 
 #include "VariantSrc.hpp"
 
+#include <cstddef>
 #include <type_traits>
 
 

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-/* Copyright 2017-2020 Fabian Koller`
	`1`	`+/* Copyright 2017-2021 Fabian Koller, Axel Huebl`
`2`	`2`	`*`
`3`	`3`	`* This file is part of openPMD-api.`
`4`	`4`	`*`
`@@ -22,6 +22,7 @@`
`22`	`22`
`23`	`23`	`#include "VariantSrc.hpp"`
`24`	`24`
	`25`	`+#include <cstddef>`
`25`	`26`	`#include <type_traits>`
`26`	`27`
`27`	`28`