Fix all compiler warnings

libs/miosix-kernel

src/tests/catch/catch-tests-entry.cpp

src/tests/catch/test-hardwaretimer.cpp

src/tests/catch/test-packetqueue.cpp

src/tests/catch/xbee/test-xbee-parser.cpp

src/tests/drivers/test-hwtimer-chain.cpp

src/tests/sensors/test-lis3mdl.cpp

src/tests/test-sensormanager.cpp