pcre, pcre2 jit libraries hang calling functions, resulting in segmentation faults

[essandess (Steve Smith)]

The pcre, pcre2 jit libraries hang when called in some situations, causing segmentation faults.

This is observed when they are used as dependencies for ​https://github.com/rspamd/rspamd.

Here's a core dump trace using pcre: ​https://github.com/rspamd/rspamd/issues/2884#issuecomment-489235483

The offending routines in this example are: sljit_free_code and _pcre_jit_compile.

See this PR for a Portfile example of the rspamd port that forces the use of the native /usr/lib/libpcre.dylib library (compiled without jit) to avoid this issue: ​https://github.com/macports/macports-ports/commit/3778fcef647b9d3cfa19f40fd4d59aa97ae1f25a

In the current rspamd build that uses native pcre, it reports in its logs:

2019-05-04 05:03:59 #69648(main) rspamd_regexp_library_init: pcre is compiled without JIT support, so many optimizations are impossible

Getting working jit in pcre and pcre2 would be great to have.