warning : even if this patch and Bug 11481 can work separately it's necessary to first install Bug 11481 in order to avoid conflict and applying patch issues.

The use of this new syspref assumes that other sysprefs OPACAllowUserToChooseBranch and canreservefromotherbranches are set on.
it introduces the following behavior about reserves :
You can't choose whatever branch as your pickup location. It must be a holding branch of an item.
Either you don't mind picking the item at one branch or another and you ask for the very first available item or you select a specific branch and you will get the first checked in item in it.
Multiholds is not possible from the pro interface (Place hold button is hidden in the results list).
In the hold form the pickup list display only the branch(es) where the items are from.
If a branch has no circulation rule allowing holds for its documents, it does not appear in the list.

Test plan :
1) Enable RequestOnOpac OPACAllowUserToChooseBranch canreservefromotherbranches and PickupHoldOnlyFromItemBranches syspref
2) Choose one borrower (patron1) to place holds : get his category, login and pasword. 
3) Go to Administration/Circulation and fine rules
4) in the ALL libraries table (selected by default) set a circulation rule for the borrower category adding an amount of holds in "Holds allowed" column
You can set only one rule for a beginning with itemtype as All or several rules with different item type.
5) In the pro interface, choose a record with some items of different branches.
6) check out some items. do not forget to checkout items on their very homebranch
7) go to opac and search for the detailed record
8) Place a hold and authenticate as patron1. In the pickup list, you must see as options, only the branches of the items. You can choose either the first available item from all these branches or first from a specific one of them. try 'first available'.
9) Go to patron1 user file and click the tab Holds : the hold had been recorded. Pickup location is 'Whatever location from the first available'.
10) reconnect as admin and check in one of the items, a message box appears : confirm the hold.
11) Reconnect as Patron1, go back to the user file and check that the pickup location zone now displays the branch of the returned item.
cancel the hold
12) redo a test from stage 6 selecting a specific branch in stage 8
13) go to pro interface to the detailed record, click the Holds tab and enter patron1 in text box
14) the holds form appears. The pickup location displays only the branches of items. Select an option and confirm the hold.
15) the holds table now display a line for the new recorded holds with patron1 name. Check that pickup location list is still restricted to item branches.