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.

Cargo.toml

@@ -5,6 +5,7 @@ version = "0.1.0"
 [dependencies]
 bitflags = "1.0.*"
 maplit = "1.0.*"
+regex = "1.1.*"
 serde = { version = "1.0.*", features = ["derive"] }
 serde_yaml = "0.8.*"
 xkbcommon = { version = "0.4.*", features = ["wayland"] }