Remove logging levels restrictions (#538)

* Fixes #537: Remove release mode logging levels restrictions;

* Add information about log's logging levels in the README;

lib/codegen/Cargo.toml

@@ -18,7 +18,7 @@ failure = { version = "0.1.1", default-features = false, features = ["derive"] }
 failure_derive = { version = "0.1.1", default-features = false }
 hashmap_core = { version = "0.1.9", optional = true }
 target-lexicon = { version = "0.0.3", default-features = false }
-log = { version = "0.4.4", default-features = false, features = ["release_max_level_warn"] }
+log = { version = "0.4.4", default-features = false }
 # It is a goal of the cranelift-codegen crate to have minimal external dependencies.
 # Please don't add any unless they are essential to the task of creating binary
 # machine code. Integration tests that need external dependencies can be

lib/codegen/meta/src/cdsl/mod.rs

@@ -1,7 +1,7 @@
 //! Cranelift DSL classes.
 //!
 //! This module defines the classes that are used to define Cranelift
-//! instructions and other entitties.
+//! instructions and other entities.
 
 pub mod types;
 

lib/codegen/src/isa/registers.rs

@@ -151,7 +151,7 @@ pub struct RegClassData {
     /// first register unit in each allocatable register.
     pub mask: RegUnitMask,
 
-    /// The global `RegInfo` instance containing that this register class.
+    /// The global `RegInfo` instance containing this register class.
     pub info: &'static RegInfo,
 }