Implement system timers

[sebastianene07]

Provide an interface to the user applications that allows timer peripheral access. Add an upper layer that manages the peripheral resource access and registers with the virtual file system as "/dev/timer" . In order to access the timers an app has to open this device and send an ioctl with the request. The upper layer will process this request and it will add the timer in a list. Applications can wait for expiration in a read() call or can ask for elapsed time by sending an ioctl.