Replaced throw() with BOOST_NOEXCEPT_OR_NOTHROW

With throw(), Visual Studio 2017 emitted a warning "C26439 SPECIAL_NOEXCEPT". Reproducible at least if code analysis was set to level: "Microsoft Native Recommended Rules".

https://docs.microsoft.com/en-us/visualstudio/code-quality/c26439?view=vs-2017

test/exception_ptr_test.cpp

@@ -87,7 +87,7 @@ exc:
         }
 
     virtual
-    ~exc() throw()
+    ~exc() BOOST_NOEXCEPT_OR_NOTHROW
         {
         --exc_count;
         }