Use the alloc crate on stable Rust

Since the minimum supported Rust version has increased to 1.36 (#193),
the alloc crate no longer requires nightly features.

Author: mbrubeck

Cargo.toml

@@ -10,7 +10,6 @@ keywords = ["hash", "no_std", "hashmap", "swisstable"]
 categories = ["data-structures", "no-std"]
 exclude = [".travis.yml", "bors.toml", "/ci/*"]
 edition = "2018"
-build = "build.rs"
 
 [dependencies]
 # For the default hasher
@@ -25,9 +24,6 @@ core = { version = "1.0.0", optional = true, package = "rustc-std-workspace-core
 compiler_builtins = { version = "0.1.2", optional = true }
 alloc = { version = "1.0.0", optional = true, package = "rustc-std-workspace-alloc" }
 
-[build-dependencies]
-autocfg = "1"
-
 [dev-dependencies]
 lazy_static = "1.2"
 rand = { version = "0.7.3", features = ["small_rng"] }

build.rs

@@ -13,8 +13,6 @@
 #![cfg_attr(
     feature = "nightly",
     feature(
-        alloc_layout_extra,
-        allocator_api,
         test,
         core_intrinsics,
         dropck_eyepatch,
@@ -35,11 +33,8 @@
 #[macro_use]
 extern crate std;
 
-#[cfg(has_extern_crate_alloc)]
 #[cfg_attr(test, macro_use)]
 extern crate alloc;
-#[cfg(not(has_extern_crate_alloc))]
-extern crate std as alloc;
 
 #[cfg(feature = "nightly")]
 #[cfg(doctest)]