vcl: add some SolarMutex assertions

Check that SolarMutex is locked after return from
Yield(), and in LazyDelete::flush().

Change-Id: I12ff312bd946b97b5f2c79169892719910884381

vcl/source/app/svapp.cxx

@@ -364,6 +364,8 @@ inline void ImplYield( bool i_bWait, bool i_bAllEvents )
     pSVData->mpDefInst->Yield( i_bWait && !pSVData->maAppData.mbAppQuit && !pSVData->maAppData.mbNoYield, i_bAllEvents );
     pSVData->maAppData.mnDispatchLevel--;
 
+    DBG_TESTSOLARMUTEX(); // must be locked on return from Yield
+
     // flush lazy deleted objects
     if( pSVData->maAppData.mnDispatchLevel == 0 )
         vcl::LazyDelete::flush();

vcl/source/helper/lazydelete.cxx

@@ -46,6 +46,8 @@ void LazyDelete::addDeletor( LazyDeletorBase* i_pDel )
 
 void LazyDelete::flush()
 {
+    DBG_TESTSOLARMUTEX(); // must be locked
+
     unsigned int nCount = lcl_aDeletors.size();
     for( unsigned int i = 0; i < nCount; i++ )
         delete lcl_aDeletors[i];