Publicbeta update 173936 for Serious Sam 3

[AlenL]

Update 173936 for Serious Sam 3 is now available in beta "publicbeta", which does not require a password.

To install the beta, do this:
- locate the game (Serious Sam 3 in this case) in the Steam's "Library" panel
- right click and invoke "Properties"
- select the "Betas" tab
- choose "publicbeta"

This has fixes and improvements for all platforms:

- Linux: Various fixes for visual artefacts caused by GPU resource corruptions that happened when game was minimized, alt-tabbed or otherwise lost focus.
- Faster switching into game after Alt-Tab, and changing Gfx APIs.
- Linux: Outdated driver versions are now reported to user on Linux.
- Linux: Fixed zombie processes sometimes being left over by the game. 
- Fixed problem where correct video mode wasn't started when changing back to game (via alt-tab) if cvar 'gfx_iAPI' is set to gfx API that is not actually supported by the platform.
- Added CPU name detection and output to console. 
- For detecting GPU vendor and device ID under Linux, "lspci" external command is now used instead of "libpci" interface. 
- OSX: Some fixes for handling of gained/lost keyboard focus. 
- Prevented possible application crash that may occur during Steam Workshop sync IO failure. 
- Handling of GPU synchronization (if gfx_iFinish>0) is now more responsive. It would sometimes cause stuttering previously.
- FPS counter variation is now also displayed (minimum and maximum frame rate for last refresh interval). Controlled via 'prf_bShowFPSVariation' cvar. (Default is on.)
- Fixed crash at start if Steam is running in offline mode. 
- Mouse is no longer confined to window after alt-enter.