Fix namespace used for hip integration, update hip and cuda examples

[m-fila]

• The integration with HIP was using boost::fiber::cuda namespace instead of boost::fiber::hip.
• The HIP examples were using very old HIP syntax (hipLaunchKernel instead of triple-chevrons or hipLaunchKernelsGGL, mandatory hipLaunchParm in kernels). I couldn't easily pinpoint the version of HIP which stopped supporting the old syntax, I propose to use the more modern version without checking compatibility with preprocessor.
• Both integration headers and examples had many unneeded headers.
• The extension of of files with HIP kernels was changed to .hip from .cpp
• Changed path to hipccc to /opt/rocm/bin as it appears to be used nowadays