[p and ]p don't account for NUL bytes

[hardenedapple]

This is more to mention it rather than ask for it to be fixed.

The s:putline() function that implements the [p and ]p mappings uses getreg() with only one argument.
This means that it receives text encoded with :help NL-used-for-Nul, and can't distinguish between NUL bytes and newlines.
After this the setreg() calls set the register contents to this encoded text, leaving the contents of the register changed.

I use NULL bytes infrequently enough that this isn't much of a bother to me, and suspect the same of others. I'm mentioning it so the information is stored somewhere.