With the flag set, the icon would be free'd twice, first by the FXSplashWindow
and then by Ruby's GC.

Remove some comments, to only from C++ usable methods

Allow more consistent read/write access to image data, that is also
usable with derived classes like FXJPGImage.

Moreover much faster String based access to the pixel data is possible,
now.

FXImage#data and FXMemoryBuffer is now deprecated.

previous swig's #setData implementation wasn't really useable