Vendors native SPICE protocol support (libguac-client-spice) from upstream
PR apache/guacamole-server#688 (GUACAMOLE-261) as patch 008, on top of the
pinned guacd (6719b20d) + existing patches. Wires --with-spice and the
libspice-client-glib-2.0-dev build dep into build-deb.sh, install.sh,
Dockerfile, and dev.sh. guacclip is kept in the source but not built
(--disable-guacclip, like guacenc/guaclog); the PR's incidental non-SPICE
terminal.c keyboard change is excluded.
guacd builds green with libguac-client-spice on Debian 13 under -Werror.
rustguac-side wiring (SessionType::Spice / SpiceParams) still to come.
Dave Kempe