Say "IR" instead of "IL".

While the specifics of these terms are debatable, "IR" generally
isn't incorrect in this context, and is the more widely recognized
term at this time.

See also the discussion in #267.

Fixes #267.

lib/frontend/src/lib.rs

@@ -1,15 +1,15 @@
-//! Cretonne IL builder library.
+//! Cretonne IR builder library.
 //!
-//! Provides a straightforward way to create a Cretonne IL function and fill it with instructions
+//! Provides a straightforward way to create a Cretonne IR function and fill it with instructions
 //! translated from another language. Contains an SSA construction module that lets you translate
-//! your non-SSA variables into SSA Cretonne IL values via `use_var` and `def_var` calls.
+//! your non-SSA variables into SSA Cretonne IR values via `use_var` and `def_var` calls.
 //!
 //! To get started, create an [`FunctionBuilderContext`](struct.FunctionBuilderContext.html) and
 //! pass it as an argument to a [`FunctionBuilder`](struct.FunctionBuilder.html).
 //!
 //! # Example
 //!
-//! Here is a pseudo-program we want to transform into Cretonne IL:
+//! Here is a pseudo-program we want to transform into Cretonne IR:
 //!
 //! ```cton
 //! function(x) {
@@ -29,7 +29,7 @@
 //! }
 //! ```
 //!
-//! Here is how you build the corresponding Cretonne IL function using `FunctionBuilderContext`:
+//! Here is how you build the corresponding Cretonne IR function using `FunctionBuilderContext`:
 //!
 //! ```rust
 //! extern crate cretonne;