Return failure trying to create v4 MAT files
Return failure trying to create v4 MAT files

* src/mat.c (Mat_CreateVer): Return NULL if mat_file_ver is MAT_FT_MAT4

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