add a test for SHMMAP and other details

[alaingdl]

The good point : a test for SHMMAP (working in GDL & IDL). Very limited but working !

The bad points (in disorder of importance) :

• my tests within SHMMAP seems to indicate that in GDL the type is not enforced .. @GillesDuvert
• INVERT and LA_INVERT in GDL (the GSL version ?) do stop when singular input. Not the expected behavior ... (a side effect of the LUDC tests to be done #1700 )
• PM #178 hum ... (the doc say no title & no format, but the code it-self ...)

(other tests are a mess : test_file_which, test_isa ...)

[codecov[bot]]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (005cc28) 41.96% compared to head (7653e04) 42.06%. Report is 2 commits behind head on master.

:exclamation: Current head 7653e04 differs from pull request most recent head 151865d. Consider uploading reports for the commit 151865d to get more accurate results

Files	Patch %	Lines
src/print.cpp	0.00%	10 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1714 +/- ## ========================================== + Coverage 41.96% 42.06% +0.10% ========================================== Files 361 361 Lines 96377 96387 +10 Branches 19815 19801 -14 ========================================== + Hits 40446 40548 +102 + Misses 55931 55839 -92 ```

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