+ BaseUnit.cpp, BaseUnit.h: new _selected flag.
+ Camera.cpp, Camera.h: linear movement has been taken over quadratic movement. Also, cursor now moves if dealing with screen borders.
+ Cursor.cpp, Cursor.h: new Cursor class holds cursor X/Y information. It is meant to be contained inside a HumanPlayer object.
* Game.cpp: minor changes in casts and comments.
+ HumanPlayer.cpp: added callbacks for button release events.
* HumanPlayer.cpp, HumanPlayerBtn.cpp: button handling has been transferred from HumanPlayer.cpp to HumanPlayerBtn.cpp in order to improve modularity.
+ Sprite.cpp: sprite data was not being checked against NULL.
- Unit.cpp: drawHandler() is now executed by Player object.
Fixed some errors in DEBUG_VAR macro.
Shadows are now drawn before any other object.
Different strings are now shown depending on the number of selected units.
Some work on calculating actions mask when different types of units are selected. Still some work TODO.
* Unit module moved from C++ to C (only extension change - and compiler - was needed).
* GfxGetHeightFromSpriteData and GfxGetWidthFromSpriteData were getting incorrect data! Incorrect memory address was being read when calling pgm_read_byte, and caused unexpected behaviour under real hw.