src/error-handling.php: Remove use of custom base-class, ErrorHandlerInvokedException, and instead use PHP-built-in class ErrorException, which seems to be intended for just this purpose (raising exceptions where PHP would ordinarily issue a notice/warning/error through its traditional error-handling system.
src/locales/countries.php: Add 'TODO' item here, about using proper cAsE for country names.
test/address.php: Just remove some commented-out stuff.
test/: Implement mock-out mechanism for calls to 'sendmail' (so the PHP 'mail' function does not actually send out any email, if a real 'sendmail' binary should actually exist on the host system); and this allows us to implement some tests for our email-related functions, which has been done.
And (finally) rename "MyPHPLibs" namespace to "SpareParts" (to be in line with the recent name-change of this library, from my-php-libs to php-spare-parts).