Fix writing v4 MAT file on big endian machine
Fix writing v4 MAT file on big endian machine

As reported by http://sourceforge.net/p/matio/bugs/33/

NJannasch/matio,tbeu/matio,MaartenBent/matio,tbeu/matio,MaartenBent/matio,NJannasch/matio,tbeu/matio,MaartenBent/matio,tbeu/matio,MaartenBent/matio