message: Fix build of grfmt_jpeg2000.cpp
  libjasper has recently changed `jas_matrix_get` from a macro to an inline function
  (389951d071 in https://github.com/jasper-software/jasper), causing the build to fail.
diff: @@ -377,7 +377,7 @@ bool Jpeg2KDecoder::readComponent8u( uchar *data, void *_buffer,
  for( y = 0; y < yend - ystart; )
  {
  - jas_seqent_t* pix_row = &jas_matrix_get( buffer, y / ystep, 0 );
  + jas_seqent_t* pix_row = jas_matrix_getref( buffer, y / ystep, 0 );
  uchar* dst = data + (y - yoffset) * step - xoffset;
  if( xstep == 1 )
  @@ -443,7 +443,7 @@ bool Jpeg2KDecoder::readComponent16u( unsigned short *data, void *_buffer,
  for( y = 0; y < yend - ystart; )
  {
  - jas_seqent_t* pix_row = &jas_matrix_get( buffer, y / ystep, 0 );
  + jas_seqent_t* pix_row = jas_matrix_getref( buffer, y / ystep, 0 );
  ushort* dst = data + (y - yoffset) * step - xoffset;
  if( xstep == 1 )
  