[ci skip] Change some log messages' level

'Class Loaded' type of messages flood log files when
log_threshold is set to 2 (debug). They're now logged
as 'info' level.

This is manually applying PR #1528, which was created
to do the same thing, but became outdated.
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 73a183b..2a61dd2 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -58,6 +58,7 @@
    -  Added support for turning newline standardization on/off via ``$config['standardize_newlines']`` and set it to FALSE by default.
    -  Added configuration setting ``$config['composer_autoload']`` to enable loading of a `Composer <https://getcomposer.org/>`_ auto-loader.
    -  Removed the automatic conversion of 'programmatic characters' to HTML entities from the :doc:`URI Library <libraries/uri>`.
+   -  Changed log messages that say a class or file was loaded to "info" level instead of "debug", so that they don't pollute log files when ``$config['log_threshold']`` is set to 2 (debug).
 
 -  Helpers