Recommend "B" flag to Apache config

Summary: Split from D1921 via D1742. The "B" flag prevents excessive unescaping, especially of "+" into " ".

Test Plan: Added "B" to server config, var_dump()'d __path__ with "+" in it, got "+" instead of " ".

Reviewers: nh, vrana, btrahan

Reviewed By: nh

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1922

src/docs/configuration/configuration_guide.diviner

@@ -89,7 +89,7 @@ this:
     RewriteEngine on
     RewriteRule ^/rsrc/(.*)     -                       [L,QSA]
     RewriteRule ^/favicon.ico   -                       [L,QSA]
-    RewriteRule ^(.*)$          /index.php?__path__=$1  [L,QSA]
+    RewriteRule ^(.*)$          /index.php?__path__=$1  [B,L,QSA]
 
     # This will use the config file you set up in the previous step. If you
     # called it something other than 'myconfig', put that here.