Issue: #615
Reported by: @moisseev

Fix build with unmodified LibreSSL opensslv.h

Add test for LibreSSL to use "old" methods when OPENSSL_VERSION_NUMBER is 0x20000000L

Issue: #613

Issue: #613

Issue: #613

* Fix parsing of URLs in texts
* Fix creating of URLs from LUA
* Fix some more URL detector issues
* Fix unit tests
* Fix JIT compilation for PCRE2 expressions
* Fix JIT usage for PCRE2
* Fix UTF8 mode in PCRE2
* Add workaround for pre-historic compilers (#605)
* Fix and rescore R_PARTS_DIFFER logic
* Properly set lua paths for tests
* Fix SA rawbody processing - exclude top part
* Store text parts content with newlines stripped
* Properly support SA body regexps
* Fix body rules in SA plugin
* Fix setting of score for parts differ
* More fixes to parts distance calculations
    - Use hashed words instead of full words for speed
    - Improve levenstein distance calculations and penalise replaces
    - Always return number from 0 to 1
    - Use g_malloc instead of alloca
* Fix percents output in R_PARTS_DIFFER
* Plug memory leak in dkim module
* Plug minor memory leak in regexps creation

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

- Use hashed words instead of full words for speed
- Improve levenstein distance calculations and penalise replaces
- Always return number from 0 to 1
- Use g_malloc instead of alloca

Reported by: @moisseev

[Minor] Improve subject rules

Make scores depend on subject length
Also resolves #548

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

Now REF_RETAIN and REF_RELEASE cannot be used for
interprocess/interthreads refcounting. However, for a single process
their performance should slightly increased.

New REF_RETAIN_ATOMIC and REF_RELEASE_ATOMIC are implemented to replace
old semantics.