Avoid accessing freed memory and freeing already freed resources

Seen in smoketest in a 4.2-based branch, but might perhaps happen in master
too. Should not hurt in any case to be more careful. ImplFreeSalGDI() is
called both from SalAbort() and from DestroySalInstance().

Change-Id: Ifac37e8ecfb432848bd3451dbda8634c59a06fba

vcl/inc/win/saldata.hxx

@@ -70,6 +70,8 @@ public:
     // checks if the menuhandle was created by VCL
     bool    IsKnownMenuHandle( HMENU hMenu );
 
+    bool                    mbResourcesAlreadyFreed;
+
 public:
     HINSTANCE               mhInst;                 // default instance handle
     HINSTANCE               mhPrevInst;             // previous instance handle

vcl/win/source/gdi/salgdi.cxx

@@ -113,6 +113,8 @@ void ImplInitSalGDI()
 {
     SalData* pSalData = GetSalData();
 
+    pSalData->mbResourcesAlreadyFreed = false;
+
     // init stock brushes
     pSalData->maStockPenColorAry[0]     = PALETTERGB( 0, 0, 0 );
     pSalData->maStockPenColorAry[1]     = PALETTERGB( 0xFF, 0xFF, 0xFF );
@@ -290,6 +292,9 @@ void ImplFreeSalGDI()
 {
     SalData*    pSalData = GetSalData();
 
+    if (pSalData->mbResourcesAlreadyFreed)
+        return;
+
     // destroy stock objects
     int i;
     for ( i = 0; i < pSalData->mnStockPenCount; i++ )
@@ -356,6 +361,8 @@ void ImplFreeSalGDI()
 
     // delete temporary font list
     ImplReleaseTempFonts( *pSalData );
+
+    pSalData->mbResourcesAlreadyFreed = true;
 }
 
 static int ImplIsPaletteEntry( BYTE nRed, BYTE nGreen, BYTE nBlue )