Cleanup: use const more, but in a way that works with pointers.

Cleanup: use const more, but in a way that works with pointers.

The standard practice is to specify const first.
In the case of pointers, anything to the left of such a declaration represents what is being pointed to.
This means const cannot be used in this case unless the pointer is intending to point to a constant.

The const qualifier may instead be put after the pointer symbol '*' to designate that the pointer and not what is being pointed to is to be a constant.

It seems that I tend to forget this behavior.
This makes a pass at existing uses of such pointers, adding const in the appropriate way.