Fix crashes caused by http authentication

[kzyapkov]

I have a sketch which consistently crashes when correct HTTP credentials are provided in the Authorization header. Experiments showed that the crashes are caused by the delete[] statements for toencode and encoded. I wasn't able to decipher the core dumps.

Trial-and-error lead to the solution here. I have no explanation why it works, but definitely fixes the world for me.

[igrr]

I'd advise against use of VLA. Since we don't have a way to reliably catch stack overflow issues, there is no way to make sure variable-length stack allocation succeeds (and crash if it fails). So it's better to use either static fixed-length arrays or dynamically allocated arrays. I think to fix the issue it is sufficient to change +1 with +2 in toencodelen calculation.

Edit: or, rather, to maintain code style, add +1 in toencode declaration:

char *toencode = new char[toencodeLen + 1];

[igrr]

#1790 (comment)

[kzyapkov]

Okay!