MeshTools: don't include STL crap in non-deprecated builds.

And only forward-declare std::tuple in the header if needed for a
deprecated signature.

src/Magnum/MeshTools/CompressIndices.cpp

@@ -27,13 +27,17 @@
 
 #include <cstring>
 #include <Corrade/Containers/Array.h>
-#include <Corrade/Containers/ArrayViewStl.h>
 #include <Corrade/Utility/Algorithms.h>
 
 #include "Magnum/Math/FunctionsBatch.h"
 #include "Magnum/MeshTools/Reference.h"
 #include "Magnum/Trade/MeshData.h"
 
+#ifdef MAGNUM_BUILD_DEPRECATED
+#include <tuple>
+#include <Corrade/Containers/ArrayViewStl.h>
+#endif
+
 namespace Magnum { namespace MeshTools {
 
 namespace {

src/Magnum/MeshTools/CompressIndices.h

@@ -37,9 +37,9 @@
 #include "Magnum/Trade/Trade.h"
 
 #ifdef MAGNUM_BUILD_DEPRECATED
-#include <tuple>
 #include <Corrade/Utility/Macros.h>
 #include <Corrade/Utility/StlForwardVector.h>
+#include <Corrade/Utility/StlForwardTuple.h>
 #endif
 
 namespace Magnum { namespace MeshTools {