CRM-21203 Fixes for Joomla 3.8+ CRON/cli and directories

[mattwire]

Work in progress fixes for Joomla 3.8 to fix cli.php and cron.php

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• CRM-21203: cli.php PHP error prevents cron jobs from running

[vingle]

I've tested this on Joomla 3.8.1 and J3.7.5 with CiviCRM 4.7.25 and confirm crons are running as expected, with no adverse behaviour.

[mattwire]

@totten Thoughts on merging? Without it civi on Joomla is a bit broken... and it doesn't seem to have any adverse effects for those who have installed. As it only touches one file it can't impact anything other than Joomla sites...

[seamuslee001]

I think the code makes sense and is limited to Joomla integration only. I have seen supportive comments in JIRA and here that this fixes the issues reported. I think this is good to merge @totten @eileenmcnaughton

[jorich-2000]

I have tried this on a couple of joomla 3.8.1 sites running under PHP 7.0.24 and 7.1.16 - although CRON runs I get a list of warnings:
/httpdocs/administrator/components/com_civicrm/civicrm/bin/cli.php" successfully completed in 1 seconds, output:

PHP Notice: Constant JPATH_ISWIN already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.legacy.php on line 64
PHP Notice: Constant JPATH_ISMAC already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.legacy.php on line 65
PHP Notice: Constant JROUTER_MODE_RAW already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.legacy.php on line 72
PHP Notice: Constant JROUTER_MODE_SEF already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.legacy.php on line 79
PHP Notice: Constant JROUTER_MODE_RAW already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.php on line 60
PHP Notice: Constant JROUTER_MODE_SEF already defined in /var/www/vhosts/nlcbanham.org.uk/httpdocs/libraries/import.php on line 67