Function show_notes::e031::concat_strings

#[no_mangle]
pub extern "C" fn concat_strings(
    first: *const c_char, 
    second: *const c_char
) -> *mut c_char

Take two strings in and concatentate them without mutating either.

This allocates a new string, which must be deallocated by calling the free_rust_string type exposed in this module.