removed "UNUSED" macro in favour of "(void)var" idiom which looks like being supported by all major compilers nowadays.
minor tweaks:
- using yield instead of sleeping 10ms because they are essentially equivalent
- slowing down cpu when waiting for an event in order to save battery
reverted formatting (every line in a makefile recipe must begin with a tab).
enabled speed optimizations under Rockbox (tested vs iRiverH320 and iPodVideo)