Engine: safer version of AGSPlatformDriver::ReplaceSpecialPaths()

Added output buffer size to parameter list.
Removed Android, iOS and PSP implementations, because they duplicated the one in the base class.
Linux: use XDG specification for special paths

As suggested by Edward Rudd.
Mutex locking guard

Added MutexLock class to prevent deadlocks. Replaced UPDATE_MP3 and UPDATE_MP3_THREAD macros with functions.
Merge pull request #115 from ivan-mogilko/fix_special_paths

Fix ReplaceSpecialPaths() and use XDG specs
Windows: do not display message window on GetPathFromCmdArg failure

Users do not need modal error window in this case, they will get a message that game files were not found anyway.
Editor: simplified GUI Alpha Style names for users' convenience
Fix for pane doesn't open after closing it by clicking the 'x' on top right.

The difference between clicking the 'x' and by clicking close in the context menu, is that for some reason clicking the 'x' fires the dock state changed event once, while closing via the context menu fires the event twice.
The code unknowingly relied on the event being fired twice since the IsShowing property of the docking container was not marked as false after showing the container was completed.
This was fixed.
debian/control: build-depend on liballegro44.-plugin-alsa (see comment).
Change ags+libraries script to work on any Debian or Ubuntu.
ags+libraries: Add comments and delete the working directory at the end.
Linux readme: Mention ags+libraries.
Debian: Remove unnecessary build dependency again and handle this in the ags+libraries script.
Engine: forward-compatible fix for gui in savedgames

When game's gui version is lower than earliest forward-compatible version - save forward-compatible version number, not latest version number.
This allows earlier interpreters to read savedgames made by later engine builds.
AGS.Native: long due fix to loaded game file version value
Manual: updated for 3.3.0 release
Editor: added new tagline
WinSetup: moved number of options to "Advanced" section
WinSetup: removed "Replay" option (it's a broken feature)
Updated build version (3.3.0.1154)
Editor: remove "beta version" tag