Too many warnings

 - Turned off GCC_WARN_64_TO_32_BIT_CONVERSION. Yes now we're ignoring warnings, but when we're ready to deal with them we can just turn it back on!
 - fixed some format strings
 - marked a variable as unused
 - removed `GCC_ENABLE_CPP_EXCEPTIONS` because we are using exceptions. It built fine for the sim, but seemed to complain when building for the device.