cleanup

example/core/string.nub

@@ -1,2 +0,0 @@
-extern func str_len(msg: string): int64;
-extern func itoa(value: int64): string;

example/program.nub

@@ -1,4 +1,4 @@
-import "core";
+import "c";
 
 global func main() {
     let x = "test";