* Add rspamd control interface:
- support `stat` command to get runtime stats of rspamd workers
- support `reload` command to reload runtime elements (e.g. sqlite3 databases)
* Rework curve25519 library for modular design:
- add Sandy2x implementation by Tung Chou
- fix CPU detection for variables loading assembly
- add testing for curve25519 ECDH
* New fixed strings library
* Add `R_SUSPICIOUS_IMAGES` rule
* Enable mmap in sqlite3
* Use new strings in the HTTP code
* Improve google perftools invocation
* Improve performance profiling in http test
* Reorganize includes to reduce namespace pollution
* Allow specific sections printing in configdump command
* Rework workers signals handlers to be chained if needed
* Update socketpair utility function
* Add control_path option for rspamd control protocol
* Fix ownership when listening on UNIX sockets
* Rework signals processing in main
* Remove extra tools from rspamd (they live in rspamadm now)
* Remove global rspamd_main
* Add global timeout for the overall task processing (8 seconds by default)
* Sanitize NULL values for fuzzy backend
* Store NM between encrypt/decrypt
* Add textpart:get_words_count method
* Fix generic DNS request in lua
* Tune hfilter weights
* Add support of IPv6 in hfilter
* Fix parsing of HTTP headers with IP addresses
* Sync with the recent libucl
* Various minor bugfixes