The base GAL has the linewidth property already, and its
accessor will only return the base version. This was causing
problems with the Cairo printing GAL, since that setter wasn't
using the base class version. Also, this removes the print-specific
setter, since the actual setting of line width shouldn't be done
there and is instead done where the drawing happens.
Fixes https://gitlab.com/kicad/code/kicad/issues/5089
CAIRO_PRINT_CTX provides a Cairo context created from wxPrintDC.
It allows one to prepare printouts using the Cairo library and
let wxWidgets handle the rest.