Let's not leak details from src/shared and src/libsystemd into
src/basic, even though you can't actually do anything useful with
just forward declarations from src/shared.
The sd-forward.h header is put in src/libsystemd/sd-common as we
don't have a directory for shared internal headers for libsystemd
yet.
Let's also rename forward.h to basic-forward.h to keep things
self-explanatory.
DNS_HOSTNAME_MAX is used by sd-resolve, but it was defined in
src/shared/dns-domain.h. The library libsystemd should be independent
of source files under src/shared.
Daan De Meyer
Yu Watanabe