Use memory type for function memory

stackframe.go

@@ -1,9 +1,15 @@
 package vm
 
-const functionMemoryEntries = 16
-
 type stackFrame struct {
 	previousFunctionIndex    int64
 	previousInstructionIndex int64
-	functionMemory           [functionMemoryEntries]uint64
+	functionMemory           *memory
+}
+
+func newStackFrame(state *State) *stackFrame {
+	return &stackFrame{
+		previousFunctionIndex:    state.functionIndex,
+		previousInstructionIndex: state.instructionIndex,
+		functionMemory:           newMemory(16),
+	}
 }