Split statistics macros into two parts: run-time and everything else.

@michaelcahill: I spent 20 minutes trying to figure out why I couldn't get any statistics for a file until I remembered that it's all triggered off statistics being configured.

This change splits the statistics macros into two flavors: run-time and everything else, that way if you open a statistics cursor on a URI without configuring run-time statistics, you can still get information about the underlying table/file.