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- the previous code used a dual-purposed graphRow for non-const/const
  access. However, clang 4.0 rightly identifies there being no
  constructor path from "graphRow<T>" to a "graphRow<const T>".

  Since the row-access is a somewhat similar concept to an STL-iterator,
  now provide non-const and const versions of the row access.

- use range-for when iterating over HashSet

- prefer forAllIters(), forAllConstIters() with automatic decltype

    containsAtPosition   -> find
    contains             -> found

    lastElement          -> last
    removeLastElement    -> remove()
    removeElement(int)   -> [TODO]  remove(int, bool)

    fcElement -> fcValue
    rcElement -> rcValue

- Eg, readIfPresent() instead of found() followed by lookup()

- use FUNCTION_NAME for IO checks

https://sourceforge.net/p/cfmesh/code/merge-requests/2/

unallocatedLabelList is not available as a typedef in OpenFOAM-dev, and UList<Type> is available everywhere

Using UPstream::commsTypes::blocking everywhere.This should work on other versions besides -dev.