Description:
------------
Unexpected behaviour for en-GB within IntlDateFormatter.

en-GB seems to render the display as a.m. for some reason? 

See output here.
https://3v4l.org/npHgN

Test script:
---------------
<?php

$date = new DateTime(null, new DateTimeZone('Europe/London'));

$france = new \IntlDateFormatter(
    'fr_FR',
    \IntlDateFormatter::NONE,
    \IntlDateFormatter::NONE,
    $date->getTimezone()
);

$uk = new \IntlDateFormatter(
    'en_GB',
    \IntlDateFormatter::NONE,
    \IntlDateFormatter::NONE,
    $date->getTimezone()
);

$us = new \IntlDateFormatter(
    'en_US',
    \IntlDateFormatter::NONE,
    \IntlDateFormatter::NONE,
    $date->getTimezone()
);

echo $france->format($date) . PHP_EOL;
echo $uk->format($date) . PHP_EOL;
echo $us->format($date) . PHP_EOL;
echo $date->format('F j, Y, g:i a');

Expected result:
----------------
20150917 11:47 AM
20150917 11:47 am
20150917 11:47 AM
September 17, 2015, 11:47 am

Actual result:
--------------
20150917 11:47 AM
20150917 11:47 a.m.
20150917 11:47 AM
September 17, 2015, 11:47 am