Add line to CHANGELOG.md

Author: James Foster

Diff for: CHANGELOG.md

@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Don't define `ostream& operator<<(nullptr_t)` if already defined by Apple
 - `CppLibrary.in_tests_dir?` no longer produces an error if there is no tests directory
 - The definition of the `_SFR_IO8` macro no longer produces errors about rvalues
+- Typo in `cpp_library.rb`, misspelling of `aux_libraries`
 
 ### Deprecated
 - `arduino_ci_remote.rb` CLI switch `--skip-compilation`