pcre2: Add JIT-support for select architectures in PCRE2

pcre2: Add JIT-support for select architectures in PCRE2

- This commit adds a config-option for JIT in libpcre2.

  According to research published on
  https://rust-leipzig.github.io/regex/2017/03/28/comparison-of-regex-engines/
  this should give a 10x performance increase on JIT operations
  which can be desireable for high performance Apache mod_rewrite
  or haproxy reqrep operations.

  This option is available on all officially supported architecutres
  which are listed on https://pcre.org/current/doc/html/pcre2jit.html#SEC2.
  Furthermore, it is enabled by default on the following
  architectures: arm, i686, x86_64.

Signed-off-by: Christian Lachner <gladiac@gmail.com>