EXT-7471 PARTIAL FIXED Ensure bottom tray chatbar can always be resized by user.

Seems, there is a problem somewhere in rendering of LLLAyoutStack children. Last visible panel marked as user_resize=true can not be resized and has no resize cursor.
Because we have no time & resources to investigate this closely a workaround is implemented for bottom tray:
 * set user_resize for layout panel with Speak button which is always visible to user;
 * set user_resize=false to don't have Speak button panel resizable.

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/438/

--HG--
branch : product-engine