Add __SCC__ macro
Add __SCC__ macro

This macro communicates to the source file being compiled
that scc is compiling it.

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