Fix no_std build.

src/fn_call.rs

@@ -17,7 +17,7 @@ use crate::stdlib::{
     iter::{empty, once},
     mem,
     num::NonZeroU64,
-    string::ToString,
+    string::{String, ToString},
     vec::Vec,
 };
 use crate::utils::combine_hashes;

src/packages/iter_basic.rs

@@ -2,6 +2,7 @@ use crate::dynamic::Variant;
 use crate::stdlib::{
     boxed::Box,
     ops::{Add, Range},
+    string::ToString,
 };
 use crate::{def_package, EvalAltResult, Position, INT};
 

src/result.rs

@@ -348,7 +348,11 @@ impl EvalAltResult {
     pub(crate) fn dump_fields(&self, map: &mut crate::Map) {
         map.insert(
             "error".into(),
-            format!("{:?}", self).split('(').next().unwrap().into(),
+            crate::stdlib::format!("{:?}", self)
+                .split('(')
+                .next()
+                .unwrap()
+                .into(),
         );
 
         match self {