Remove direct stackSize modification check

markDirty needs to be called when stackSize is modified directly (which
is ugly and nobody should do it, ever). Without calling markDirty, this
is a serious bug and will cause problems with other inventories,
including item duplication, which *can* be done on will.
Merge branch '1.7.10' of https://github.com/copygirl/BetterStorage into 1.7.10