[Analysis] Make LocationSize pretty-printing more descriptive

This is the third patch in a series intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context. The second being r344013.

The intent is to make the output of printing a LocationSize more
precise. The main motivation for this is that we plan to add a bit to
distinguish whether a given LocationSize is an upper-bound or is
precise; making that information available in pretty-printing is nice.

llvm-svn: 344108