[sldev] Code review on first branding patch (VWR-13726)

[Rob Lanphier]

Hi folks,

I've got a first branding patch for Snowglobe. 
http://jira.secondlife.com/browse/VWR-13726

This changes the taskbar icon, the titlebar name, and a few other
places.  A new "VIEWER_NAME" macro is introduced, but not used yet
(saving for another patch suitable for merging into the main SL Viewer).

Notes:  I've only built/tested this on Linux.

Rob