Split cgen()
Split cgen()

This function will be too big, so it is better to split it in several
functions and to use a jump table. Yes, yes, I know is more efficient
the big case, but I cannot manage it.

8l/scc,k0gaMSX/scc,8l/scc,k0gaMSX/scc,k0gaMSX/kcc,k0gaMSX/kcc,k0gaMSX/scc,8l/scc