Release 2.3

Release 2.3

* [Conf] SPF is no longer a C module
* [Conf] Update spamtrap map path example
* [CritFix] Fix html entities decoding
* [CritFix] Fix re cache when mix of pcre and hyperscan is used
* [Feature] Allow milter code to deal with multiple headers
* [Feature] Antivirus: Add avast support
* [Feature] Dkim_signing: Allow to sign via milter_headers
* [Feature] Implement content hashes
* [Feature] Lua_text: Add regexp split iterator method
* [Feature] Lua_text: Implement flattening of the input tables
* [Feature] Send quit command to Redis
* [Feature] Speed up is_ascii function
* [Feature] Spf: Add external_relay option
* [Fix] Avoid double escaping
* [Fix] Fix O(N^2) algorithm
* [Fix] Fix arc seal validation
* [Fix] Fix base tag processing according to stupid HTML renderer behaviour
* [Fix] Fix dealing with `\0` in ucl strings and JSON
* [Fix] Fix gpg parts misdetection
* [Fix] Fix ignored symbols exporting
* [Fix] Fix processing of numeric url's
* [Fix] Fix processing of the closed tcp connections
* [Fix] Fix regexp type check for pcre2
* [Fix] Fix urls encode function
* [Fix] Fix urls shifting when doing decode to include separators
* [Fix] Fix white on white rule and add is_leaf flag
* [Fix] Further fixes in charset detection
* [Fix] Ignore diacritics in chartable module for specific languages
* [Fix] Limit size of symbols options by max_opts_len option
* [Fix] More fixes in html tag content calculations
* [Fix] Plug memory leak in fuzzy storage
* [Fix] Process high priority settings even if settings/id has been specified
* [Fix] Select a different upstream on last retransmit
* [Fix] Treat soft hyphen as zero width space
* [Fix] Try harder to watch the lifetime of the key_stat
* [Fix] Use ipv6-mapped-ipv4 addresses in radix trie
* [Project] Add logic to break execution when processing symbols*
* [Project] Add methods to set specific content for mime parts from Lua
* [Project] Lua_content: support PDF files
* [Project] Move dns_tool to using of the rspamd_spf from FFI module
* [Project] Preliminary SPF plugin in Lua
* [Project] Show debug stat for memory pool
* [Project] Some rework about specific data that is now tagged
* [Project] Start reworking of the mempool structure
* [Rework] Allow to add userdata as symbols options
* [Rework] Change mime part specifics handling
* [Rework] Move LRU SPF cache from spf plugin
* [Rework] Rework HTML tags content attachment
* [Rework] Rework options hash structure
* [Rework] Start lua_content library
* [Rework] Stop using of uthash for http headers
* [Rework] Use faster hashing approach for memory pools variables
* [Rules] Add PDF related rules

Signed-off-by: Vsevolod Stakhov <vsevolod@highsecure.ru>