Allow terminating the VM

src/virtualmachine/VirtualMachine.cpp

@@ -196,6 +196,11 @@ namespace vm
 		return 1;
 	}
 
+	void VirtualMachine::End()
+	{
+		PC = romSize+1;
+	}
+
 	int VirtualMachine::Call(int address)
 	{
 		word w;

src/virtualmachine/VirtualMachine.h

@@ -120,6 +120,7 @@ public:
 		int LoadProgram(char * filename);
 		int Run();
 		int Call(int address);
+		void End();
 		void Marshal(int address, word element)
 		{
 			ram_t * ptr = ram+RP+address;