psxy: Add broken arrows

[joa-quim]

From (new) docs

When used together with -Sv (Cartesian vectors), the x and y directives produce broken (right-angle elbow) arrows: instead of a straight line from tail to tip, the vector is drawn along two perpendicular legs meeting at a corner. x draws the horizontal leg first, then the vertical leg; y draws the vertical leg first, then the horizontal leg. The arrowhead is placed at the tip.

Co-authored (mostly) by Claude.

Example

echo 0 0 45 3 | build\src\gmt psxy -R-5/5/-5/5 -JX10c -Sv0.3c+e -Ay -W1p -Gred -Ba -png lixo

Note, the test/psxy/elbowvec.sh file needs to be set to execution mode (I can't do it)

[github-actions]

Summary of changed images

This is an auto-generated report of images that have changed on the DVC remote

Status	Path
added	test/baseline/psxy/elbowvec.ps
modified	test/baseline/psxy/

Image diff(s)

Details

Added images

• test/baseline/psxy/elbowvec.png

Modified images

Path	Old	New

Report last updated at commit c10caea

[Esteban82]

It works.