CRM-14355 test to check existing behaviour of alternate syntaxes

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* CRM-14355: make api treat limit = 0 as an unlimited request
  http://issues.civicrm.org/jira/browse/CRM-14355
CRM-14355 alter behaviour to do an unlimited retrieve if ['options']['limit'] (or a legacy variant) is set but has an empty value

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* CRM-14355: make api treat limit = 0 as an unlimited request
  http://issues.civicrm.org/jira/browse/CRM-14355