store the value to be set inside wxON_BLOCK_EXIT_SET(), this allows to use temporaries with it and also fixes the test failure when built with icc and optimizations on (not sure if it is a compiler bug or not but in any case it seems better to fix it)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56848 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/scopeguard.h

@@ -131,6 +131,9 @@ wxScopeGuard wxMakeGuard(F func, P1 p1, ..., PN pN);
     }
     @endcode
 
+    Notice that @a value is copied, i.e. stored by value, so it can be a
+    temporary object returned by a function call, for example.
+
     @see wxON_BLOCK_EXIT_OBJ0(), wxON_BLOCK_EXIT_NULL()
 
     @header{wx/scopeguard.h}