message: build: eliminate warning
  warning: 'layout.channel_layout::gchan' may be used uninitialized in this function [-Wmaybe-uninitialized]
diff: @@ -487,7 +487,7 @@ bool PAMDecoder::readData( Mat& img )
  bool res = false, funcout;
  PaletteEntry palette[256];
  const struct pam_format *fmt = NULL;
  - struct channel_layout layout;
  + struct channel_layout layout = { 0, 0, 0, 0 }; // normalized to 1-channel grey format
  /* setting buffer to max data size so scaling up is possible */
  AutoBuffer<uchar> _src(src_elems_per_row * 2);
  @@ -506,9 +506,7 @@ bool PAMDecoder::readData( Mat& img )
  layout.bchan = 0;
  layout.gchan = 1;
  layout.rchan = 2;
  - } else
  - layout.bchan = layout.gchan = layout.rchan = 0;
  - layout.graychan = 0;
  + }
  }
  CV_TRY
  