- Rename kernel.c -> kernel.cpp and uart.c -> uart.cpp
- Add universalisos::uart namespace with constexpr register definitions
- Use extern "C" linkage for kernel_main() called from boot.S
- Compile with arm-none-eabi-g++ using C++17 freestanding flags
(-fno-exceptions, -fno-rtti, -fno-threadsafe-statics, -fno-use-cxa-atexit)
- Update Makefile to use g++ and .cpp build rules