stack: revise acs_call() API
acs: move acs API declarations here
function: move declaration of function types here
machine: move opcode and bscalls to header
stack: remove unused code
fixup! machine: move opcode and bscalls to header
machine: change acs_call_tail() api
machine: introduce acs_global()
machine_test: move machine tests here
stack: remove unused code
machine: substitute with stack machine
machine: create variable in acs_global()