Maintain Pear Coding Standard in class Net_URL2

- According to PHPCS Pear Coding Standard
- Fixed typos
- Fixed PHP Code Inspections (PHPStorm)
Removed superfluous data

Removed duplicated array key/value pair.

- Not the first example data anyway (RFC 3986, section 5.4)
Rest of the code using single quotes

Rest of the code used single quotes, but not every rest of the
code. This has been fixed now.

- Single quotes are used in code
- Double quotes are used in comments
Fix: Remove preg_replace /e modifier

Since longer in PHP trunk and then with upcomming PHP 5.5, the
preg_replace() /e modifier is deprecated. Instead, the
preg_replace_callback() function is used.

- Add test for normalize() method which is subject to changes
- Added private _normalizeCallback method
- Changed preg_replace() to preg_replace_callback()