Fix memory leak of structure fieldnames from HDF5 files
Fix memory leak of structure fieldnames from HDF5 files

* src/mat73.c (Mat_H5ReadGroupInfo): Free the elements of fieldnames and
      free fieldnames itself

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