/nojit: /dfa: engine-specific options

[rurban]

support engine-specific options in cperl, like /nojit: /dfa:
and handle it there.

new rx options:

• //no_jit:
• //dfa:

PCRE has some specific pcre2syntax (*NO_JIT) option, which is not supported upstream though.
(*LIMIT_MATCH=d), (*LIMIT_DEPTH=d), ...
See http:https://www.pcre.org/current/doc/html/pcre2syntax.html#SEC16

[todd-richmond]

supporting dfa would be a help for issues where perlre regexes can take infinitely long (URI::Find::Schemeless for example). An example simple config mechanism to enable options is the one re::engine::RE2 uses