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/filetests/src/test_legalizer.rs

@@ -1,4 +1,4 @@
-//! Test command for checking the IL legalizer.
+//! Test command for checking the IR legalizer.
 //!
 //! The `test legalizer` test command runs each function through `legalize_function()` and sends
 //! the result to filecheck.

lib/filetests/src/test_print_cfg.rs

@@ -1,6 +1,6 @@
 //! The `print-cfg` sub-command.
 //!
-//! Read a series of Cretonne IL files and print their control flow graphs
+//! Read a series of Cretonne IR files and print their control flow graphs
 //! in graphviz format.
 
 use std::borrow::Cow;

lib/filetests/src/test_verifier.rs

@@ -1,4 +1,4 @@
-//! Test command for checking the IL verifier.
+//! Test command for checking the IR verifier.
 //!
 //! The `test verifier` test command looks for annotations on instructions like this:
 //!