build: Remove SPICE_SERVER_INTERNAL definition building

The only part we use this feature is including the generated enumerations for debugging purposes. Update and use the templates we have for enumerations to remove this requirements. Doing so we are sure that SPICE server is seeing the same header version as any other software. Also Meson defined it for all project while Autoconf was using it only for server directory.

Signed-off-by: Frediano Ziglio fziglio@redhat.com