gcl0x: Give error for unterminated blocks and comments
gcl0x: Give error for unterminated blocks and comments

- Blocks must be terminated within their own segment
- Comments must be terminated at the end

kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom,kervinck/gigatron-rom