Is it possible to get Eclipse Mars 4.5.0 IDE for C/C++ to show the filenames of the functions in the call hierarchy. For example in the below view I would like to see the name of the file that the "IncrementCount" and "DecrementCount" is in.
Reason is most functions are called from numerous files and I would like to see them listed here instead of clicking each function to open the files.

There is currently no option to get the Call Hierarchy view to display filenames for results.
As a workaround, you could consider using "Find References" instead (right-click -> References -> Workspace or Ctrl+Shift+G). This is like one level of the Call Hierarchy (i.e. it shows you the callers, but not the callers of the callers), and the callers are grouped by file.
That said, I don't see a reason the Call Hierarchy view shouldn't show filenames. Consider filing an issue asking for this to be added.