Remove CS_MODE_N64

- This mode is for the so-called MIPS "N64" ABI; it has nothing to do with the Nintendo 64 game platform.
- N64, O64, et al. are just different ABIs for the 64-bit MIPS architecture, so we replace CS_MODE_N64 with the existing CS_MODE_64
docs: add a link to online doc of cs_disasm_iter()
Merge branch 'improvement/remove_mips_n64' of https://github.com/parasyte/capstone into mips
Merge branch 'next' of https://github.com/aquynh/capstone into next
Merge branch 'mips' into next