locale: Add translations for layout names

Pulled in some Unix-specific code from https://github.com/rust-locale/locale_config to reduce dependencies.

First reason to reduce dependencies: gettext-rs is not in Debian. Copying gettext-sys might have made sense, but the interface is somewhat confusing.

For translating a couple identifiers, detection and some hand-rolled hash map is all that is needed, and the option to move to gettext later remains.

locale_config has been stripped of the lazy_static dependency, which, messing with the strtup sequence, might be a source of debugging woes. Plus setting language once in the beginning is somewhat inflexible regarding runtime changes.

src/locale.rs

@@ -0,0 +1,39 @@
+/*! Locale-specific functions */
+
+use std::cmp;
+use std::ffi::CString;
+
+mod c {
+    use std::os::raw::c_char;
+
+    #[allow(non_camel_case_types)]
+    pub type c_int = i32;
+
+    #[no_mangle]
+    extern "C" {
+        // from libc
+        pub fn strcoll(cs: *const c_char, ct: *const c_char) -> c_int;
+    }
+}
+
+fn cstring_safe(s: &str) -> CString {
+    CString::new(s)
+        .unwrap_or(CString::new("").unwrap())
+}
+
+pub fn compare_current_locale(a: &str, b: &str) -> cmp::Ordering {
+    let a = cstring_safe(a);
+    let b = cstring_safe(b);
+    let a = a.as_ptr();
+    let b = b.as_ptr();
+    let result = unsafe { c::strcoll(a, b) };
+    if result == 0 {
+        cmp::Ordering::Equal
+    } else if result > 0 {
+        cmp::Ordering::Greater
+    } else if result < 0 {
+        cmp::Ordering::Less
+    } else {
+        unreachable!()
+    }
+}