[bug #65561] Projections to infinity in Warp

[Giacomo Lorenzetti]

Follow-up Comment #4, bug #65561 (group gnuastro):

Sorry, the steps written in the first message are not correct. Here are the
correct ones:

$ astarithmetic 5000 5000 2 makenew 10 mknoise-sigma -o img.fits
$ astwarp img.fits --shear=0.2 --project=0.001,0.0005


The difference with the introductory message is in the pic's size: small
figures are not affected by the bug (given those shear and project values).
The reason is that in the mentioned case the problematic points are on a line
with a negative slope and a positive intercept, hence affected pics are those
that are big enough to "touch" that line.

Regarding the fix, we have decided a different approach, that doesn't led to
an error message but that ignore those pixels, with negligible effects on the
output.
Incidentally, we have found an optimization. It is implemented in a different
commit, given that it doesn't seem to have an active role in solving the bug.
The optimization highlights a misbehaviour (already present): it doesn't seem
to affect sensibly the output, hence it will be addressed later, with low
priority.

The suggested commits are stored in this branch:
https://gitlab.cefca.es/glorenzetti/gnuastro/-/tree/warp_speedup_pr?ref_type=heads
(The fix alone is also present in the divzero_pr branch, if needed)


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