scanner: prepend protocol name to types symbol

When doing unity builds via meson (example project:
https://github.com/swaywm/sway

) multiple source files are glued together
via #include directives. Having every wayland-scanner generated source
file have an identifier named '*types[]' will lead to errors in these
unity builds if two or more of these are joined.

Signed-off-by: Marty E. Plummer <hanetzer@startmail.com>