Improve ColumnDefinition comparison performance

We have already improved the performance here for the basic comparison, however since these happen exceedingly frequently we may as well go a little (easy step) further. This is a really tiny patch, and we should aim to include before GA, but not RC.

Right now we use all of an int for the metadata presorting, but in fact we only need 2-3 bytes for this. We can upcast the int to a long, and use the remaining bits to store the prefix of the name. This way, a majority of comparisons become a single long comparison. Which will be considerably cheaper.