If I send money to a friend in prison every month. Is this considered support?

It’s a gift. 

Your friend is being supported by the state.  You are just sending a gift.

No.  You are not supporting your friend and cannot deduct anything or claim your friend as a dependent.  The money you send is a gift.  Gifts to individuals are not deductible.  Your friend's support is being provided by the department of corrections (and the taxpayers of the U.S.).