What is the ruling on one who posts pictures or statuses on WhatsApp that contain supplications such as "O Lord, grant me provision, heal me," intending thereby to complain to people, not to Allah, and is this considered shirk (polytheism)?

It is permissible to post remembrances (dhikr) and supplications (du'a) on WhatsApp status, as long as there is no Sharia-based prohibition in them, such as transgressing in supplication. As for informing someone of one's illness or poverty, if it is merely for information, there is no harm. However, if the intention behind it is to complain and object to Allah's decree, then this is reprehensible and contradicts patience. A Muslim aims to complain of their worries and needs to Allah alone.