FTBFS with GCC 14 due missing incompatible pointer types

Hi,

Fedora 40 prepares introduction of GCC 14 and it was found out hplip fails to build from source with the newest GCC due using incompatible pointers.

Mostly it is the case when non-const pointer is assigned into const one, so the solution is to explicitly convert to const, or when passing generic pointer to pointer into argument expecting void pointer to pointer, where conversion does not happen as well. The solution here is to assign the generic pointer into temp void pointer, pass its address into function and assign the temp void pointer into generic pointer in the end.

The patch fixing the issue is attached and it works for GCC 13.2.1 as well - would you mind applying it to the project? In case there are problems with the patch, do let me know.

Thank you in advance!

Zdenek