Fixed by having LLViewerMedia::updateMediaImpl() copy the media entry's current URL into the media impl's mMediaURL in the case where the impl has a non-empty media URL but the function doesn't do a navigate.

Review #33

This change marks the current selection "not editable" if
any objects in the selection are currently "in flight" (i.e.
their media data has not been fetched yet, or is in the
process of being fetched).  This involved adding API to
LLMediaDataClient to query whether an object is in the
process of being fetched (i.e. in the queue).  I've added
a unit test for this new API.

EXT-2082   	 Multifloater preview tab container extends outside window border
EXT-773   	 odd notecard behaviour on closing an unsaved notcard
reviewed by Richard

The Search URL now includes a "r=" query parameter to specify the
user's preferred maturity rating. This can be "pg" or "pg,mature"
or "pg,mature,adult".

Added accessors to get platform-specific process ID from LLProcessLauncher.

Added an optional "debug" argument to LLPluginClassMedia::init() and LLPluginProcessParent::init() (defaults to false).

Mac only: made the state machine in LLPluginProcessParent::idle() open a new window in Terminal.app with a gdb session attached to the plugin process upon successful launch.

Asking for help (e.g., pressing F1) before logging in will now display
a specific pre-login help topic, "pre_login_help". This behavior was
agreed upon with Rand to allow us to display a custom page to help the
user log on successfully.