Issue 399 rebased

[zbeekman]

Avg response time	coverage on master

Summary of changes

Fix issue #399. Really implementing a function get_by_ref for allocatable components.

Rationale for changes

Previous implementation was errorneous and to expensive w/o any benefit.

Additional info and certifications

This pull request (PR) is a:

• Bug fix
• Feature addition
• Other, Please describe:

I certify that

• I have reviewed the contributing guidelines and followed the
  policies on:
  - Pull request (PR) naming to indicate work in progress (WIP),
  and to attach the PR to the appropriate bug report, or feature
  request issue
  - White space (no trailing white space or white space errors may
  be introduced)
  - Commenting code where it is non-obvious and non-trivial
  - Running tests locally, to ensure all of them pass
  - Maintaining or increasing test coverage
  - Logically atomic, self consistent and coherent commits
  - Commit message content
  - Waiting 24 hours before self-approving the pull request to
  give another OpenCoarrays developer a chance to review my
  proposed code

[codecov]

Codecov Report

Merging #430 into master will increase coverage by 1.32%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #430      +/-   ##
==========================================
+ Coverage   38.05%   39.38%   +1.32%     
==========================================
  Files           3        3              
  Lines        1997     2105     +108     
  Branches      330      350      +20     
==========================================
+ Hits          760      829      +69     
- Misses       1127     1154      +27     
- Partials      110      122      +12

[zbeekman]

LGTM

Content virtually identical to previous PR and issue-399 branch. Diff after rebasing issue-399 on top of current master verifies this. "Self approving" ahead of the 24 hour period, but this is really Andre's work.