Bump version to 2.4.0
Merge branch 'upgrade/irmp'
IRMP: Remove unused files

This removes all files of the IRMP release which are not used making the
whole package more leightweight. Furthermore it is now easier to import
the project into an IDE, as IRMP don't need to be excluded from the build.
Merge branch 'cleanup/irmp'
uart_protocol.c: Remove empty line
uart_protocol.c: Refine Doxygen comments
uart_protocol.h: Refine Doxygen comments
Merge branch 'refine/uart-protocol'