Fixing whitespaces errors

I've used script `whiter examples lib xt t` from the module https://metacpan.org/module/Test::Whitespaces to fix all problems with whitespaces.

Here is the list of rules that Test::Whitespaces uses:

 * Each line ends with "\n" (including the last line)
 * For new lines "\n" is used (not "\r\n")
 * There are no ending spaces on the lines
 * 4 spaces are used instead of tabs
 * No empty lines in the end of file