Signed-off-by: Daniela Engert <dani@ngrt.de>

Parameterize 'printf(rgb color, ...)' and 'vprint_rgb(rgb color, ...)' on the type of the format string.
Signed-off-by: Daniela Engert <dani@ngrt.de>

- Disable templated user-defined literals when compiled under nvcc

Similarly to Intel's C++ compiler, nvcc fails to compile templated UDLs
as they both share the same parsing engine (EDG C++ Front End).  This
fixes building CUDA programs which make use of fmt.

Changed "reusing existing formatters example" to use scoped enum instead.