Renamed llviewerversion to llversioninfo, to avoid confusion with
llversionviewer in llcommon (llversion is already used by llwindow).
Created new LLVersionInfo class with the following methods:
static S32 getMajor();
static S32 getMinor();
static S32 getPatch();
static S32 getBuild();
static const std::string &getVersion();
static const std::string &getShortVersion();
static const std::string &getChannel();
All viewer code has been updated to use this API. Viewer code no
longer directly includes llversionviewer.h from llcommon.
Arrehn