[test] check whether default-constructed forward iterators compare equal

Since C++14, default-constructed forward iterators are specified as the end iterator of the same, empty sequence. Hence, they should compare equal. This patch enhances our test accordingly.

changed milestone to %DUNE 2.6.0

added feature label

added Testing label

added 2 commits

• d23c69ec - [bugfix] initialize pointer to list in ArrayList iterators
• adaffa63 - [test] check whether default-constructed forward iterators compare equal

Compare with previous version

Note: This MR makes YaspGrid fail the grid tests.

added 33 commits

• adaffa63...22d3a9df - 31 commits from branch master
• 8a9f01c6 - [bugfix] initialize pointer to list in ArrayList iterators
• bba00364 - [test] check whether default-constructed forward iterators compare equal

Compare with previous version

The issue in for YaspGrid is fixed in dune-grid!248 (merged), which makes all dune-grid tests pass for me locally.

mentioned in commit a4c439ec

merged

mentioned in commit 6920f0d5

mentioned in merge request !396 (merged)