extern declarations without an explicit ABI are deprecated

[coolbutuseless]

While building I get some warnings about "extern declarations". Adding in the "C" as suggested silenced these warnings.

• R 4. 5.0
• rustc 1.87.0 (17067e9ac 2025-05-09) (Homebrew)

   warning: extern declarations without an explicit ABI are deprecated
    --> src/random.rs:4:5
     |
   4 | pub extern fn random_number() -> i32 {
     |     ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`
     |
     = note: `#[warn(missing_abi)]` on by default
   
   warning: extern declarations without an explicit ABI are deprecated
    --> src/mythreads.rs:5:5
     |
   5 | pub extern fn run_threads() {
     |     ^^^^^^ help: explicitly specify the "C" ABI: `extern "C"`

[jeroen]

Thanks. Do you want to send a PR?