#1063 Rust Lexer updates

[SiegeLord]

These patches update the Rust lexer to the newest Rust features:

• Naked CR can now be escaped in strings.
• If the file starts with these 3 characters: #![ then that does not count as a hashbang comment.
• Added byte-string literals (b'x', b"x" and br"x"), which are similar to existing string literals but with some restrictions on their contents.

The SciTE patch adds the styles for the byte-string literals and updates the keyword list.

[Neil Hodgson]

Committed first 3 as [8b0ea8], [14e632], and [3b6ac6].

Bumping the copyright year isn't really needed and I no longer do it. Having the year of origin is useful. As an individual, copyright lasts for 50 or more years after your death depending on jurisdiction. Its not based on the date of the last change. If you really want to update the year that is fine but, to me, its just commit noise.

An issue with the Rust lexer came up recently because of a shadowed variable warning in [feature-requests:#1059]. There are 2 variables called old_pos in ScanNumber and their lifetimes do not make sense.

[SiegeLord]

Thanks, and understood about the copyright year.

I'll send you a patch for the warning asap.

[SiegeLord]

Ok, here's the patch to fix that shadowing issue. I notice that it's quite tricky to detect these variable shadowings, as even adding a -Wshadow did not make GCC (4.8.1) and Clang (3.3) report any warnings for that variable.

Also, while reviewing the code I've noticed that I've neglected to comment it as much as I should have, perhaps unduly reducing the maintainability of this. Would you accept patches adding some comments here and there?

[Colomban Wendling]

That's because of [f8ff456eeb5878cbdd2c557eca76d6090696d2d2] I guess, because on 3.4.4 it showed just fine, either with GCC 3.8 or 3.9 at least.

[Neil Hodgson]

Committed as [85a5b4].

Whatever level of comments you are happy with is fine. To me, a reference to the language syntax definition being used would be more helpful.