Make the casting work on Windows too.

Fixes CppunitTest_starmath_qa_cppunit on Windows.

Change-Id: I3fd73db1ebb70ac19f99bc3e337b1a8107486ae7
diff --git a/framework/source/services/frame.cxx b/framework/source/services/frame.cxx
index 230707c..54850af5 100644
--- a/framework/source/services/frame.cxx
+++ b/framework/source/services/frame.cxx
@@ -129,7 +129,9 @@ enum EActiveState
    @devstatus  ready to use
    @threadsafe yes
*//*-*************************************************************************************************************/
class Frame :   // interfaces
class Frame :
                public  ::cppu::OWeakObject                         ,   // helper implements XInterface, XWeak
                // interfaces
                public  css::lang::XTypeProvider                    ,
                public  css::lang::XServiceInfo                     ,
                public  css::frame::XFrame2                         ,
@@ -145,8 +147,7 @@ class Frame :   // interfaces
                // Order is necessary for right initialization of this class!
                public  ThreadHelpBase                              ,
                public  TransactionBase                             ,
                public  PropertySetHelper                           ,   // helper implements ThreadHelpbase, TransactionBase, XPropertySet, XPropertySetInfo
                public  ::cppu::OWeakObject                             // helper implements XInterface, XWeak
                public  PropertySetHelper                               // helper implements ThreadHelpbase, TransactionBase, XPropertySet, XPropertySetInfo
{
public: