File stale path references.

After rearranging the directory layout, some paths in documentation
needed updating.

Fix some typos too.

lib/cretonne/meta/build.py

@@ -1,6 +1,6 @@
 # Second-level build script.
 #
-# This script is run from src/libcretonne/build.rs to generate Rust files.
+# This script is run from lib/cretonne/build.rs to generate Rust files.
 
 from __future__ import absolute_import
 import argparse

lib/cretonne/meta/gen_build_deps.py

@@ -1,7 +1,7 @@
 """
 Generate build dependencies for Cargo.
 
-The `build.py` script is invoked by cargo when building libcretonne to
+The `build.py` script is invoked by cargo when building lib/cretonne to
 generate Rust code from the instruction descriptions. Cargo needs to know when
 it is necessary to rerun the build script.
 

lib/cretonne/meta/gen_types.py

@@ -2,7 +2,7 @@
 Generate sources with type info.
 
 This generates a `types.rs` file which is included in
-`libcretonne/ir/types/rs`. The file provides constant definitions for the most
+`lib/cretonne/ir/types.rs`. The file provides constant definitions for the most
 commonly used types, including all of the scalar types.
 
 This ensures that Python and Rust use the same type numbering.