stdlib checks do not allow dereferencing the first element of a vector
when there are no elements in the vector (regardless of whether we have
allocated memory for them). This whole function is rather
over-engineered, setting up multiple allocations and branches depending
of the string size. This commit reduces the function to the actions
needed (get the string size, print it into the output)
Only special strings starting with a dot are supported. Parsing of concatenated special strings using quotes needs to be implemented, but at least a few test-cases are already there now.
While the bug has been fixes, the winding handling in the
SetArcGeometry() function isn't tested. This adds a regression
test on EDA_SHAPE, which is where the logic now lives.
Relates-To: https://gitlab.com/kicad/code/kicad/-/issues/15694
Jon Evans
Roberto Fernandez Bautista
Seth Hillbrand
Thomas Pointhuber
John Beard
Marek Roszko