Update information about git-p4

It was moved out of contrib in git-1.7.11.
git fast-import doesn't need to be run in Git directory.
Make two timestamps in diff output more distinct.

It takes time to scan over two dates in the output to find out what is
the difference between them. And then a reader may wonder why the
new version is older then the previous one. So make two timestamps
more distinct to avoid unnecessary eyeballing of the example output.
This change improves readability a bit.
Make '#' and parentheses valid characters in URLs.

This makes makepdf recognize wikipedia-style links in the text.
One such URL was added to chapter 4 in commit e644082f43.
makeebooks: Allow translators to translate the book title, comments.
Merge pull request #346 from GArik/EN

Miscelaneous small corrections