Bump version for user guide
Bump version for user guide

* documentation/matio_user_guide.texi: Bump version to 1.5.2

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