Add the suffix _type for the C structures in GLS

[amontoison]

@nimgould Is it fine for you?
It doesn't concern the code in Fortran, it's just the structures in the C interface that are renamed.
I always need some sed commands in the Julia interface because of this missing suffix.
Only GLS is concerned by this "issue".

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.84%. Comparing base (a4377f1) to head (32cb121).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #362   +/-   ##
=======================================
  Coverage   41.84%   41.84%           
=======================================
  Files         325      325           
  Lines      167628   167628           
  Branches    58076    58076           
=======================================
  Hits        70143    70143           
  Misses      79992    79992           
  Partials    17493    17493           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[nimgould]

I am not completely happy with this as it is breaking change for any C user who already uses the gls package. Of course, this may be nobody! OK, let's do it, and I'll divert any grumbles to you :)