Issue 80 in svnbook: ch04: Incorrect definition of revision

[svnbook at googlecode.com]

Updates:
	Status: Done

Comment #6 on issue 80 by ptbu... at gmail.com: ch04: Incorrect definition of  
revision
http://code.google.com/p/svnbook/issues/detail?id=80

Chapter 4 probably isn't the place to get into a comprehensive discussion  
of libsvn_fs_*'s storage mechanisms vs. a user's view of a revision (and  
everything in-between)...so in r3896 I simply changed the language to be  
similar to that in svn.basic.in-action.revs.