py, compiler: Clean up and compress scope/compile structures.

Convert int types to uint where sensible, and then to uint8_t or
uint16_t where possible to reduce RAM usage.
py, compile: Combine have_star_arg, have_dbl_star_arg into star_flags.

Small reduction in ROM, heap and stack usage.
py, compile: Reduce size of compiler structure.
py, compile: Simplify initialisation of compiler structure.