tree-wide: remove Emacs lines from all files This should be handled fine now by .dir-locals.el, so need to carry that stuff in every file.

util-lib: split out allocation calls into alloc-util.[ch]

hashmap: refactor hash_func All our hash functions are based on siphash24(), factor out siphash_init() and siphash24_finalize() and pass the siphash state to the hash functions rather than the hash key. This simplifies the hash functions, and in particular makes composition simpler as calling siphash24_compress() repeatedly on separate chunks of input has the same effect as first concatenating the input and then calling siphash23_compress() on the result.

hashmap: introduce hash_ops to make struct Hashmap smaller It is redundant to store 'hash' and 'compare' function pointers in struct Hashmap separately. The functions always comprise a pair. Store a single pointer to struct hash_ops instead. systemd keeps hundreds of hashmaps, so this saves a little bit of memory.

shared: switch our hash table implementation over to SipHash SipHash appears to be the new gold standard for hashing smaller strings for hashtables these days, so let's make use of it.

Add set_consume which always takes ownership Freeing in error path is the common pattern with set_put().

shared: add simple priority queue implementation