remove oniguruma from the dependencies as mdcat now uses the pure rust
regex backend

On x86, the stack protector was disabled by addinsg
`-fno-stack-protector` to CFLAGS. This was due to rust not passing
`-lssp_nonshared` to the linker, causing build errors while linking.

Rust has been patched to fix this issue, so now we can enable stack
protection again.

https://github.com/lunaryorn/mdcat
Cat for markdown