Consider translation of transformation matrix of image rotation

[Regina Henschel]

Hi Armin, hi all,

this is about https://bugs.documentfoundation.org/show_bug.cgi?id=115590 
and my proposal https://gerrit.libreoffice.org/#/c/50176/

It works in principle, but I'm not sure about some details:

A
It has a construction
     basegfx::B2DHomMatrix aFullTransform;

     with later on
     if ( !aFullTransform.isIdentity() )

Should I use
     basegfx::B2DHomMatrix aFullTransform;
     bool bHasTransformation;

     if ( bHasTransformation )
instead?

B
It has
     if ( aTransformedCenterPosition != aCenterPosition )
Is this check useful, or should I calculate the correction always, 
although the result might be the original value?

C
Is this the correct place at all to correct the position?

Kind regards
Regina