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/cretonne/src/binemit/memorysink.rs

@@ -20,7 +20,7 @@ use std::ptr::write_unaligned;
 
 /// A `CodeSink` that writes binary machine code directly into memory.
 ///
-/// A `MemoryCodeSink` object should be used when emitting a Cretonne IL function into executable
+/// A `MemoryCodeSink` object should be used when emitting a Cretonne IR function into executable
 /// memory. It writes machine code directly to a raw pointer without any bounds checking, so make
 /// sure to allocate enough memory for the whole function. The number of bytes required is returned
 /// by the `Context::compile()` function.