Fix two Cppcheck warnings (constVariablePointer)

Make variables more local, especially move them into for loops.
Fixes four Cppcheck warnings (variableScope, redundantAssignment,
shadowVariable).

Two instances found by Cppcheck (variableScope).
Reduced variable scope and put together variable declaration
and initialization in surrounding code.

Found by Cppcheck (unreachableCode).

Remove code deprecated in 2.9 or earlier

See merge request !233

.. and its flags `FROM_BOTTOM` and `FROM_TOP`.

Remove the file ugtime.h

See merge request !232

'true' and 'false' are just as readable.

They are not used anywhere, and if we should need timers again
in the future, then the timer code from dune-common would be
a better choice.

It is not actually used.

Remove argument from cmake command finalize_dune_project

See merge request !231

Simplify the control_word handling

See merge request !229

The control word code has been vastly simplified, and I don't think we
will need the debug code ever again.

This avoids an 'unused variable' compiler warning.

That code was never enabled in Dune times.  It was somehow related
to matrix connections, and matrices don't exist anymore anyway.

These are never used.

It is never used anywhere else.

Its values are trivial now.

It is not used.

This makes the code more readable, by getting rid of numbers in the code
that seem like magic until you understand what they mean.

Unfortunately, this patch triggers a new warning about offsetof being
only 'conditionally supported'.  The code seems to work though.
Apparently, the warning may go away with C++20

(see http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0545r0.html)

And I still don't like the code that uses the offsetof.  I may
replace that by something better in the future.

This method doesn't even exist anymore.  Nobody noticed the call
was still there because it was hidden behind some old DEBUG flag.

It is not used.

These are not used anymore.  This also allows to remove a lot of
global macros.

It is not used.