Avoid a signed int overflow (UB)
Avoid a signed int overflow (UB)

With compiler option: `-fsanitize=undefined`, we get:
> ../../platforms/iOS/vm/OSX/SqViewClut.m.inc:87:52: runtime error: left shift of 65280 by 16 places cannot be represented in type 'int'

timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm