sasl: Make this crate no_std

We mostly had to import from alloc some structs that are part of the std
prelude, such as Vec and String.

sasl/src/common/mod.rs

@@ -1,5 +1,7 @@
-use std::collections::BTreeMap;
-use std::string::FromUtf8Error;
+use alloc::borrow::ToOwned;
+use alloc::collections::BTreeMap;
+use alloc::string::{FromUtf8Error, String};
+use alloc::vec::Vec;
 
 #[cfg(feature = "scram")]
 pub mod scram;

sasl/src/common/scram.rs

@@ -1,3 +1,7 @@
+use alloc::string::{String, ToString};
+use alloc::vec;
+use alloc::vec::Vec;
+use core::fmt;
 use getrandom::{getrandom, Error as RngError};
 use hmac::{digest::InvalidLength, Hmac, Mac};
 use pbkdf2::pbkdf2;
@@ -25,8 +29,8 @@ pub enum DeriveError {
     IncompatibleIterationCount(u32, u32),
 }
 
-impl std::fmt::Display for DeriveError {
-    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+impl fmt::Display for DeriveError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match self {
             DeriveError::IncompatibleHashingMethod(one, two) => {
                 write!(fmt, "incompatible hashing method, {} is not {}", one, two)
@@ -40,7 +44,7 @@ impl std::fmt::Display for DeriveError {
     }
 }
 
-impl std::error::Error for DeriveError {}
+impl core::error::Error for DeriveError {}
 
 impl From<hmac::digest::InvalidLength> for DeriveError {
     fn from(_err: hmac::digest::InvalidLength) -> DeriveError {