* Added keyboard.h to cpctelera_all.h
* Improved example makefiles: now they take all .c source files from src/
* Changed function name from readFullKeyboardStatus to scanKeyboard
* Added new scanKeyboardFast function, that improves performance by unrolling the loop
* Added isKeyPressed function, which checks if a concrete key is pressed or not, by looking at results of scanKeyboard
* Added new example to examples/ folder: readKeyboard
** It scans the keyboard and checks if SPACE key is pressed. When it is pressed, a concrete sprite is printed, and a different one is printed when SPACE is not pressed.