ext/ldap: few new unit tests (tls13 protocol).

[devnexen]

No description provided.

[nielsdos]

I think a better idea is to split each of these tests into two files based on whether the constant is defined. Because now we're skipping on older versions, although that may be no a big deal. Wdyt?

[devnexen]

alright, gonna split it.

[nielsdos]

There's some redundancy now between the tests, an option could be to add version checks to the files such that only one variant of the two is executed.
But I think this is good enough.