improve readability

and make it easier to debug.
top crasher in 5.3.0.3 is around this area:
https://cgit.freedesktop.org/libreoffice/core/tree/vcl/source/gdi/
bmpacc2.cxx?h=libreoffice-5.3.0.3#n235

http://crashreport.libreoffice.org/stats/signature/
BitmapReadAccess::GetPixelForN32BitTcRgba(
unsigned%20char%20const%20*,long,ColorMask%20const%20&)#summary

in case someone wonders suffix increment '++' precedes dereference '*'

Change-Id: I15876711db569d55739da3514f61ef1b981269ab
Reviewed-on: https://gerrit.libreoffice.org/35099Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>

vcl/source/gdi/bmpacc2.cxx

@@ -127,7 +127,8 @@ BitmapColor BitmapReadAccess::GetPixelForN24BitTcBgr(ConstScanline pScanline, lo
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetBlue( *( pScanline = pScanline + nX * 3 )++ );
+    pScanline = pScanline + nX * 3;
+    aBitmapColor.SetBlue( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetRed( *pScanline );
 
@@ -136,7 +137,8 @@ BitmapColor BitmapReadAccess::GetPixelForN24BitTcBgr(ConstScanline pScanline, lo
 
 void BitmapReadAccess::SetPixelForN24BitTcBgr(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + nX * 3 )++ = rBitmapColor.GetBlue();
+    pScanline = pScanline + nX * 3;
+    *pScanline++ = rBitmapColor.GetBlue();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline = rBitmapColor.GetRed();
 }
@@ -145,7 +147,8 @@ BitmapColor BitmapReadAccess::GetPixelForN24BitTcRgb(ConstScanline pScanline, lo
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetRed( *( pScanline = pScanline + nX * 3 )++ );
+    pScanline = pScanline + nX * 3;
+    aBitmapColor.SetRed( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetBlue( *pScanline );
 
@@ -154,7 +157,8 @@ BitmapColor BitmapReadAccess::GetPixelForN24BitTcRgb(ConstScanline pScanline, lo
 
 void BitmapReadAccess::SetPixelForN24BitTcRgb(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + nX * 3 )++ = rBitmapColor.GetRed();
+    pScanline = pScanline + nX * 3;
+    *pScanline++ = rBitmapColor.GetRed();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline = rBitmapColor.GetBlue();
 }
@@ -163,7 +167,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcAbgr(ConstScanline pScanline, l
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetBlue( *( pScanline = pScanline + ( nX << 2 ) + 1 )++ );
+    pScanline = pScanline + ( nX << 2 ) + 1;
+    aBitmapColor.SetBlue( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetRed( *pScanline );
 
@@ -172,7 +177,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcAbgr(ConstScanline pScanline, l
 
 void BitmapReadAccess::SetPixelForN32BitTcAbgr(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + ( nX << 2 ) )++ = 0xFF;
+    pScanline = pScanline + ( nX << 2 );
+    *pScanline++ = 0xFF;
     *pScanline++ = rBitmapColor.GetBlue();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline = rBitmapColor.GetRed();
@@ -182,7 +188,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcArgb(ConstScanline pScanline, l
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetRed( *( pScanline = pScanline + ( nX << 2 ) + 1 )++ );
+    pScanline = pScanline + ( nX << 2 ) + 1;
+    aBitmapColor.SetRed( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetBlue( *pScanline );
 
@@ -191,7 +198,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcArgb(ConstScanline pScanline, l
 
 void BitmapReadAccess::SetPixelForN32BitTcArgb(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + ( nX << 2 ) )++ = 0xFF;
+    pScanline = pScanline + ( nX << 2 );
+    *pScanline++ = 0xFF;
     *pScanline++ = rBitmapColor.GetRed();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline = rBitmapColor.GetBlue();
@@ -201,7 +209,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcBgra(ConstScanline pScanline, l
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetBlue( *( pScanline = pScanline + ( nX << 2 ) )++ );
+    pScanline = pScanline + ( nX << 2 );
+    aBitmapColor.SetBlue( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetRed( *pScanline );
 
@@ -210,7 +219,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcBgra(ConstScanline pScanline, l
 
 void BitmapReadAccess::SetPixelForN32BitTcBgra(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + ( nX << 2 ) )++ = rBitmapColor.GetBlue();
+    pScanline = pScanline + ( nX << 2 );
+    *pScanline++ = rBitmapColor.GetBlue();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline++ = rBitmapColor.GetRed();
     *pScanline = 0xFF;
@@ -220,7 +230,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcRgba(ConstScanline pScanline, l
 {
     BitmapColor aBitmapColor;
 
-    aBitmapColor.SetRed( *( pScanline = pScanline + ( nX << 2 ) )++ );
+    pScanline = pScanline + ( nX << 2 );
+    aBitmapColor.SetRed( *pScanline++ );
     aBitmapColor.SetGreen( *pScanline++ );
     aBitmapColor.SetBlue( *pScanline );
 
@@ -229,7 +240,8 @@ BitmapColor BitmapReadAccess::GetPixelForN32BitTcRgba(ConstScanline pScanline, l
 
 void BitmapReadAccess::SetPixelForN32BitTcRgba(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    *( pScanline = pScanline + ( nX << 2 ) )++ = rBitmapColor.GetRed();
+    pScanline = pScanline + ( nX << 2 );
+    *pScanline++ = rBitmapColor.GetRed();
     *pScanline++ = rBitmapColor.GetGreen();
     *pScanline++ = rBitmapColor.GetBlue();
     *pScanline = 0xFF;