Drop a a few accidentally repeated words

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

doc/clients-howto

@@ -264,7 +264,7 @@ The following IDs occur:
   rejects redirections in batch files.
 
   Certain bad failures make the server ignore the rest of the batch
-  file file.  This feature is too hard to predict to be really useful.
+  file.  This feature is too hard to predict to be really useful.
 
   Protocol flaw: strictly asynchronous clients cannot support
   C_EXECUTE correctly.  By the time C_EXECUTE arrives, the client may
@@ -286,7 +286,7 @@ The following IDs occur:
 
   empire-client prints the text verbatim, prepended by a line feed.
   This is clearly sub-optimal, because it can be inserted in the
-  middle of user input.  Clients wishing to to display asynchronous
+  middle of user input.  Clients wishing to display asynchronous
   messages together with normal I/O should insert them before the
   current prompt.
 

doc/contributing

@@ -22,7 +22,7 @@ install the "git-core" package.  You can always download from
 
 If you're new to git, try the gittutorial(7) manual page, and the Git
 User's Manual.  Both are also available at <http://git-scm.com/>,
-along with other resources, including the the "Pro Git" book.
+along with other resources, including the "Pro Git" book.
 
 
 Getting sources

doc/threads

@@ -50,7 +50,7 @@ The server has seven basic threads:
 		while the update is in progress.
 	select:
 		This thread and its interface provides a mechanism for
-		other threads to deschedule until either a a file descriptor
+		other threads to deschedule until either a file descriptor
 		is read/write ready, or a particular amount of time has passed.
 		When the select thread actually runs, the whole process
 		blocks until the select system call returns.  However,