Fix email address in matdump help string
Fix email address in matdump help string

* tools/matdump.c (helpstr): Change email address to sourceforge

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