Macro rust_icu_sys::versioned_function

macro_rules! versioned_function {
    ($i:ident) => { ... };
}

This library was build with version renaming, so rewrite every function name with its name with version number appended.

The macro will rename a symbol foo::bar to foo::bar_XX (where “XX”) is a string coming from the environment variable RUST_ICU_MAJOR_VERSION_NUMBER, which is expected to be defined at compile time.