Enable functions to use global imports.

doc/src/language/fn-namespaces.md

@@ -82,8 +82,9 @@ fn get_message() { "Hello!" }
 | script.rhai |
 ---------------
 
+import "message" as msg;
+
 fn say_hello() {
-    import "message" as msg;
     print(msg::get_message());
 }
 say_hello();

doc/src/language/fn-ptr.md

@@ -77,7 +77,6 @@ f::do_work();               // works!
 let p = Fn("f::do_work");   // error: invalid function name
 
 fn do_work_now() {          // call it from a local function
-    import "foo" as f;
     f::do_work();
 }