Add value- and char-array support to co_reduce functions.

[vehre]

Add support for recude-functions with value parameters.
Add support for char-arrays as arguments to reduce-functions.
Rename co_reduce_1 to internal_co_reduce to get a better naming.
Create mpi-datatype to transport the char-array length.
Improved cleanup of co_broadcast. Fixed co_reduce_string testcase.

Fixes #172.

[vehre]

@zbeekman: On your comments on the previous pull request:

• I left the comment in the CMakeLists.txt intentionally, because not only the commented phrase should be deleted, but also the testcases should be moved to the regular unit test directory once the patch is approved.
• Its of course possible to use my editor to use space instead of tabs, but I don't see why :-), because there is no common style in the code and jumping over a tab while coding is far more easier than over 8 spaces.
• I had trouble to amend the commit to fix the copyrightCLA and resolved this by producing a diff, throwing the whole commits away, applying the patch to a fresh master and commiting that. So no, I don't know how to amend a commit. And I don't care after working for more than 12 hours today.
• Fixing style sometimes happens just because I had some debugging in there. So when deleting the debuging again a style change may occur.

You use my limited time for fixing bugs and adding features or for fixing style. Your choice! :-)

[codecov-io]

Codecov Report

Merging #332 into master will increase coverage by 0.48%.

@@            Coverage Diff             @@
##           master     #332      +/-   ##
==========================================
+ Coverage   45.73%   46.22%   +0.48%     
==========================================
  Files           3        3              
  Lines        1019     1045      +26     
  Branches      193      201       +8     
==========================================
+ Hits          466      483      +17     
- Misses        476      483       +7     
- Partials       77       79       +2

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[zbeekman]

@zbeekman: On your comments on the previous pull request:

I left the comment in the CMakeLists.txt intentionally, because not only the commented phrase should be deleted, but also the test cases should be moved to the regular unit test directory once the patch is approved.

OK, you could probably have included it with the patch, but that's fine

Its of course possible to use my editor to use space instead of tabs, but I don't see why :-), because there is no common style in the code and jumping over a tab while coding is far more easier than over 8 spaces.

Obviously you don't use Emacs ;-p

I had trouble to amend the commit to fix the copyrightCLA and resolved this by producing a diff, throwing the whole commits away, applying the patch to a fresh master and commiting that. So no, I don't know how to amend a commit. And I don't care after working for more than 12 hours today.

That's perfectly acceptable... your approach is fine

Fixing style sometimes happens just because I had some debugging in there. So when deleting the debuging again a style change may occur.
You use my limited time for fixing bugs and adding features or for fixing style. Your choice! :-)

well I'm happy to clean up after you, at least until I get a better handle on the gfortran internals etc.... :-)

[zbeekman]

LGTM