Provide support for PCRE2

[minhtrancccp]

As shown in the instruction to make a PCRE-supported binary, the devel lib of older PCRE is required (which is not made clear from the instruction's text).
Since PCRE is no longer developed by its own maintainers from 2021, as well as a wider adoption for PCRE2 by other projects (such as PHP or grep), I think it would be appropriate for nnn's devs to migrate to PCRE2 instead, or at least to make a note on which PCRE version to be used in the make process.

[jarun]

Please raise a PR.