Fix bug linearly indexing cell arrays
Fix bug linearly indexing cell arrays

* src/matvar_cell.c (Mat_VarGetCellsLinear): Use start as the starting
      index to read from

MaartenBent/matio,tbeu/matio,CBL-ORION/matio,martinichka/matio-coder,NJannasch/matio,CBL-ORION/matio,NJannasch/matio,tbeu/matio,tbeu/matio,martinichka/matio-coder,CBL-ORION/matio-sf-mirror,MaartenBent/matio,telehan/libmatio,martinichka/matio-coder,telehan/libmatio,MaartenBent/matio,tbeu/matio,MaartenBent/matio,CBL-ORION/matio-sf-mirror