string.padded-zeros keeps a leading minus in front of the zeros but not a leading plus: "+42" becomes "00+42" #9038

string.padded-zeros keeps a leading minus sign in front of the zeros, but not a leading plus sign:

"-42".padded-zeros 5   -> "-0042"
"+42".padded-zeros 5   -> "00+42"

"00+42" is not a number any more, "00+42".as-number fails. "+42".as-number and "%d".scanf "+42" both accept the plus sign, so a text with it is a valid number in the rest of the library.

What should happen: a leading + is kept in front of the zeros the same way - is, giving "+0042".