- Removed the regular expression check for IP addresses since QUrl/KUrl now

  correctly parse almost all short url addresses.
- Create the remaining QRegExp checks once instead of on demand.
- Use KUser for username name and directory shortcuts, e.g. ~/, resolution.
- Percent-encoded extra '@' within a URL's username component (Workaround).
- Added unit tests for IPv6 URLs and escaping of '@' in usernames.

BUG: 69326
BUG: 118413
FIXED-IN: 4.6.5
REVIEW: 101576

(cherry picked from commit d1101e6d)