reviewed by Stone

EXP-1160 FIX Cannot drag/drop items from inventory into the contents of a prim in latest Mesh build 239475
brought back some old logic for dispatching to child folder as drag and drop fallback

Added comment where sidebar block list is opened.

Made changes per RB feedback.

STORM-638 FIXED "Object Return" didn't return distant objects if the confirmation dialog wasn't suppressed.

Reason: Showing the confirmation dialog resets object selection,
thus there is nothing to derez.

Fix: Save selection until user answers in the confirmation dialog.

I didn't investigate why the bug occurred only for distant object
(must be some internal LLSelectMgr magic).

Addressing review feedback.

Fix LLInstanceTracker::key_iter constructor param; accepting
InstanceMap::iterator by non-const reference relied on Microsoft extension
that accepts non-const reference to an rvalue. Given typical iterator
implementation, simply accept by value instead, which makes gcc happy too.

Updating patch to current version of viewer-development

The regression was introduced in the fix of EXP-856 (changeset 9e650f2750b5).

It turned out impossible to properly remove an inventory item
from within LLDiscardAgentOffer::done(), because that would lead to
nested LLInventoryModel::notifyObservers() calls.

Fixed that by deferring removal until the next LLAppViewer::idle() iteration.

Also elimiteed duplicated code.

When auto-discarding inventory offers we looked up missing Busy button
(i.e. a button having index=3) in the inventory offer notification dialog
template. Failure to find the button resulted in ignoring inventory offers.

Fixed that by "auto-clicking" the existing Discard button.

Reason:
In case of deferred upgrade (i.e. when you select "Later...") the defaults for notifications settings are not loaded,
so when the viewer exits after launching the updater, it incorrectly re-saves notifications settings.

Fix:
Initialize settings earlier, so that viewer picks them up in update mode.