[task #15578] Function to find if polygon vertices are sorted anti-clockwise

[Mohammad Akhlaghi]

Follow-up Comment #13, task #15578 (project gnuastro):

Some small points:

* I see that the returned type of the declaration of
`gal_polygon_to_counterclockwise' is still `void', but it has been fixed in
the definition. Do you try compiling these? There should have been a
compilation warning. Note that in Gnuastro, we aim to have no compilation
warnings ;-).

* To help in readability (this is just stylistic), I usually write these
statements like below (so the `sum' conditions are right under each other and
more clear to the eye.


  if      (sum <0) return GAL_POLYGON_ORIENTATION_CCW;
  else if (sum==0) return GAL_POLYGON_ORIENTATION_COMPLEX;
  else             return GAL_POLYGON_ORIENTATION_CW;


But even a cleaner implementation would be like this, avoiding all the dirty
`if's and `else's and `returns':


  return ( sum
           ? ( sum < 0
               ? GAL_POLYGON_ORIENTATION_CCW
               : GAL_POLYGON_ORIENTATION_CW )
           : GAL_POLYGON_ORIENTATION_COMPLEX );


* Given that the natural sign of `sum' is negative when the orientation is
counter-clockwise, it may be better and more clear if the values of
`GAL_POLYGON_ORIENTATION_CCW' and `GAL_POLYGON_ORIENTATION_CW' are
interchanged so they are natural.

After these changes, I think it is good enough for testing. Please correct the
documentation. 

Then add a test usage of these library functions in the Crop program (just
before the line `if(crp->p->polygonnosort)' in `polygonmask' of `onecrop.c'):
with a few checking `printf's after it, followed by an `exit 0;'.

Then please add a few example calls to the `--polygon' option in
`tests/during-dev.sh' and commit/push it so I can also try them easily. 

The basic idea is that the newly added `polygonnosort' option should be
reversed (replaced): we should be able to automatically see if the given
polygon is sorted or not. If it is, we won't change/touch it. If it isn't
we'll sort it. But the user can manually request a sorting with a new
`--polygonsort' option, in which case, we won't do any sorting checks at all,
and will directly call the `gal_polygon_ordered_corners'.

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