Updated version 3.3 new features in welcome pane
Makefile: removed PIE and FPIE compile flags for Linux
Engine: corrected Theora playing callback
Script: restored compatibility with plugins, creating managed objects

I had to add new PluginObject type of script variable, to distinct it from "normal" DynamicObject.
First, it should not make use of wrapper helpers for reading/writing values, because plugin interface does not declare such functionality, and read and write directly by memory address, as it was done for all objects in vanilla AGS.
Second, member function calls should be handled using vanilla way of calling functions.
Script: added PluginArgument script value type

When plugin calls a script function, it casts all parameters to 32-bit ints. If an adress of managed object was passed in such a way, script interpreter should know that it is allowed to use this value as one.
Common, Engine: fixed few pointer conversion warnings
Editor: additions and corrections for the welcome page text
Editor: updated splash bitmap (version 3.3)
Saving layout.xml to App Data folder

To avoid crash when not running as administrator and installing into
program files, using best practices described by Microsoft and saving
the layout file in the application data folder instead the executable
folder.
Merge branch 'master' of https://github.com/adventuregamestudio/ags
Android: Fixed disparity between displayed and real values in the preferences.
Common: Fixed missing printf argument.
Common: Fixed missing return statements.
Linux: Added blue cup icon.
Merge branch 'master' into develop