Use hex escape sequences instead of octal escape sequences

[Mingun]

Octal escape sequences the least used form of escape sequences and hex supported almost everywhere. The only outsiders are Java (does not support \xHH form), C++ (unlimited length, so have problems with followed digits) and Rust (limited range of representable characters -- only [0x00; 0x7f]).

Seriously, who decided that using octal escape sequences by default was a good idea?

I've checked all languages and everything (except Java and Rust) are support \xHH form.

[Mingun]

This is ready for review.