urlencode can't process unicode chars like '↓' or '–' (long dash)

[DirkSchmitt]

Using urlencode from debian package gridsite-clients 3.0.0~20180202git2fdbc6f-3+b1.

1. urlencode '–' → %FF%FF%FF
2. urlencode ' ↓' → %FF%FF%FF
3. urlencode '– ↓' → malloc(): corrupted top size

If not fixed, this malfunction should IMHO be documented clearly in the manpage.