Version Control With Subversion Source

(Changesets): Use the standard "rN" syntax for revision numbers.
(Keeping a Branch in Sync): Don't change verb subject in mid-sentence.
Say "these changes", not "your changes", because the changes in
question were by someone else and only merged to "your" branch.
Add an extra update step in example, to emphasize the point.
Clarify some things by introducing the term "line of development".
(Mergeinfo and Previews): Don't claim we saw 'svn mergeinfo'
earlier, since this is actually the first mention of it.