Added a fix for a 'garbage/undefined value' bug reported by clang.  in var.c, when varp->shape was being allocated, it was not being initialized properly and as a result, in some circustances, could potentially be dereferenced and evaluated without having a proper value.  It is now initialized to 0. Hopefully this does not cause a problem. All the tests continue to pass, but I'm leaving a verbose comment here in case there is a knock-on problem discovered somewhere down the line.