Develop>XUI>Send Test IMs: Lets not poke fun of a resident tradition in the public beta. Also it should test a sentence that wraps. Ideally it would also test a string with double-byte characters but I dont know how to do that.

The active parcel media instance always gets priority over other inworld media.

Created LLViewerMediaImpl::unload(), which unloads the media and clears internal state (such as the last-navigated URL) to keep it from getting reloaded.

LLViewerMedia::updateMediaImpl() now calls unload() on the impl instead of just using destroyMediaSource().

Made LLViewerMedia::updateMediaImpl() unload the impl's media plugin when the current URL goes empty.

Made LLVOVolume::syncMediaData() call removeMediaImpl() if the media data gets deleted.

Sending now works.
Reviewed with Ambroff.

Disabled saving notifications to disk because the load code hasn't worked for months, it spams the logs, and it hits the disk.
Discussed with Q, the author.

Reviewed with Ambroff

These changes had been made last month, but got smooshed.

Added a version field at the beginning of inventory cache files.  If version field is not found or does not match expectected value, then the cache is discarded.  In 1.23, the version line triggers a warning but is otherwise ignored.

Reviewed by Seraph.

For EXT-2335 Diagnose warning spam: "LLInventoryPanel::buildNewViews called with invalid objectp->mType"

Trivial fix to just ignore reading in items that have unknown/none asset type.

problem was caused by triggering updateMeshTextures() every time visual params
or textures were changed on your base avatar object. The latest structure
makes the parameters and textures in the wearables authoritative, causing them
to be copied to the avatar on a regular basis. This resulted in way too many callbacks
to be registered while waiting for baked textures to be uploaded.

Fixed by removing many calls to updateMeshTextures() and ensuring that it gets called
every time an appropriate param or texture actually changes, or a wearable gets
added/removed. This appears to cut the number of callbacks to a reasonable level.

Code reviewed by Bigpapi.

As requested by the search team.

- we'll be managing its state rather manually, not necessarily conforming to 'toggle' semantics.

Various trivial UI behavioral changes for disabling/enabling old/new floaters when bringing up properties of objects/items.
This is to make the UI behavior compliant with the Inventory Panel MVP.

Also added missing sidepanel_task_info.xml (although this is not actually enabled for viewer2.0).

Don't have LLVoiceClient manually poke the nearbychatbar's 'speak' button's visual state as a special case
- all speak buttons will soon know how to poll (sigh) the ptt state, with more reliability.