Remove non-standard abort() calls in tests

[rouson]

With the aim of making OpenCoarrays viable for use with multiple compilers, please ensure that all code that hits the master branch is standard-conforming. An example of non-standard code is the "call abort()" appearing throughout the test suite, including but definitely not limited to the following locations:

1. Line 26 of get_with_offset_1d.f90.
2. Line 45 and other lines in get_array_test.f90.
3. Line 173 and other lines in old_get_array_test.f90.
4. Line 133 of sameloc.f90.

and many other locations. Presumably these only terminate a single image and should therefore be replaced with stop. Alternatively, if global termination is intended, they should be replaced with error stop.

If there is a compelling reason to include non-standard code in the repository, let's document it. I will submit a separate issue to help address the state of documentation in the tests.

[rouson]

@vehre and @afanfa

Item 1 in the above list is the one current test failure when building OpenCoarrays with the GCC 7 trunk dated 20161026. GitHub shows the two of you as contributors to the relevant file: get_with_offset_1d.f90. Please address the above issue in that file and any others to which you contributed.