shared: make sure foo.bar and foobar result in different domain name hashes This also introduces a new macro siphash24_compress_byte() which is useful to add a single byte into the hash stream, and ports one user over to it.

basic: include only what we use This is a cleaned up result of running iwyu but without forward declarations on src/basic.

siphash: minor coding style fixes and modernizations Only cosmetics really, doesn't change any actual logic.

siphash24: let siphash24_finalize() and siphash24() return the result directly Rather than passing a pointer to return the result, return it directly from the function calls. Also, return the result in native endianess, and let the callers care about the conversion. For hash tables and bloom filters, we don't care, but in order to keep MAC addresses and DHCP client IDs stable, we explicitly convert to LE.

siphash24: change result argument to uint64_t Change the "out" parameter from uint8_t[8] to uint64_t. On architectures which enforce pointer alignment this fixes crashes when we previously cast an unaligned array to uint64_t*, and on others this should at least improve performance as the compiler now aligns these properly. This also simplifies the code in most cases by getting rid of typecasts. The only place which we can't change is struct duid's en.id, as that is _packed_ and public API, so we can't enforce alignment of the "id" field and have to use memcpy instead.

siphash24: unify API Make the API of the new helpers more similar to the old wrapper. In particular we now return the hash as a byte string to avoid any endianness problems.

siphash24: expose the internal helper functions

build-sys: split internal basic/ library from shared/ basic/ can be used by everything cannot use anything outside of basic/ libsystemd/ can use basic/ cannot use shared/ shared/ can use libsystemd/