COMP: Do not also pass png_ptr twice to png_set_error_fn
COMP: Do not also pass png_ptr twice to png_set_error_fn

To address the warning from GCC 8:

/ITK/Modules/IO/PNG/src/itkPNGImageIO.cxx: In member function 'void
itk::PNGImageIO::WriteSlice(const string&, const void*)':
/ITK/Modules/IO/PNG/src/itkPNGImageIO.cxx:583:20: warning: passing
argument 1 to restrict-qualified parameter aliases with argument 2
[-Wrestrict]
   png_set_error_fn(png_ptr, png_ptr,
                       ^~~~~~~  ~~~~~~~

Which appears to have identified a bug. The function signature is:

png_set_error_fn(png_structp png_ptr, png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warning_fn);

LucasGandel/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,richardbeare/ITK,malaterre/ITK,BRAINSia/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,LucasGandel/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,blowekamp/ITK,blowekamp/ITK,LucasGandel/ITK,Kitware/ITK,thewtex/ITK,fbudin69500/ITK,richardbeare/ITK,malaterre/ITK,malaterre/ITK,BRAINSia/ITK,Kitware/ITK,fbudin69500/ITK,hjmjohnson/ITK,LucasGandel/ITK,blowekamp/ITK,vfonov/ITK,thewtex/ITK,LucasGandel/ITK,hjmjohnson/ITK,BRAINSia/ITK,malaterre/ITK,vfonov/ITK,malaterre/ITK,fbudin69500/ITK,fbudin69500/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,malaterre/ITK,hjmjohnson/ITK,hjmjohnson/ITK,fbudin69500/ITK,vfonov/ITK,thewtex/ITK,LucasGandel/ITK,blowekamp/ITK,fbudin69500/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,richardbeare/ITK,vfonov/ITK,vfonov/ITK,BRAINSia/ITK,hjmjohnson/ITK,malaterre/ITK,Kitware/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,BRAINSia/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,Kitware/ITK,blowekamp/ITK,vfonov/ITK,Kitware/ITK,vfonov/ITK,blowekamp/ITK,thewtex/ITK,vfonov/ITK,Kitware/ITK,LucasGandel/ITK,richardbeare/ITK,Kitware/ITK,BRAINSia/ITK,blowekamp/ITK,hjmjohnson/ITK,blowekamp/ITK,fbudin69500/ITK,fbudin69500/ITK,vfonov/ITK,BRAINSia/ITK