Remove the value assigned to a global variable in state
Examples: (makunbound-global 'y state) General Form: (makunbound-global s state)
This value returned is the result of modifying the ACL2 state so that the given symbol does not have a value. This function thus acts as a no-op if the symbol does not have a value in the given state. Also see related utilities f-get-global, f-put-global, and f-boundp-global.