[FEATURE REQUEST] Add missing string manipulation functions

[AdrianVovk]

Many things in gstrfuncs.h don't have wrappers. Most importantly, I need g_str_tokenize_and_fold to implement searching in my app.

Other missing functions I've run into:

• g_str_match_string
• g_str_to_ascii
• Potentially others

[AdrianVovk]

Also, g_str_tokenize_and_fold has an optional out variable, so maybe something like this:

fn tokenize_and_casefold_internal(
    arg: &str,
    translit_locale: Option<&str>,
    alts: bool
) -> (glib::StrV, Option<glib::StrV>) {
    // https://github.com/gtk-rs/gtk-rs-core/issues/1418
    use glib::translate::*;
    arg.run_with_gstr(|arg| {
        translit_locale.run_with_gstr(|translit_locale| {
            let mut alternates: *mut *mut std::ffi::c_char = std::ptr::null_mut();
            let alternates_ptr = if alts {
                &mut alternates
            } else {
                std::ptr::null_mut()
            };
            unsafe {
                let result = glib::ffi::g_str_tokenize_and_fold(
                    arg.to_glib_none().0,
                    translit_locale.to_glib_none().0,
                    alternates_ptr
                );
                (
                    glib::StrV::from_glib_full(result),
                    alts.then(|| glib::StrV::from_glib_full(alternates))
                )
            }
        })
    })
}

pub fn tokenize_and_casefold(arg: &str) -> glib::StrV {
    tokenize_and_casefold_internal(arg, None, false).0
}

pub fn tokenize_and_casefold_with_alts(
    arg: &str,
    translit_locale: Option<&str>
) -> (glib::StrV, glib::StrV) {
    let res = tokenize_and_casefold_internal(arg, translit_locale, true);
    (res.0, res.1.unwrap())
}

[sdroege]

It would seem more useful to use Rust APIs for this kind of tasks. If you want to provide a PR that adds bindings for the functions, I'd review that, but it doesn't seem very useful to me. Rust string parsing functions in std and external crates are generally better.