fix register use in putstring

was off by one, the syscall is write 
and the first arg is file_descriptor
ie 1 == stdout

lib/slot_machine/macro/putstring.rb

@@ -3,8 +3,8 @@ module SlotMachine
     def to_risc(compiler)
       builder = compiler.builder(compiler.source)
       integer = builder.prepare_int_return # makes integer_tmp variable as return
-      word = Risc.syscall_reg(1).set_compiler(compiler)
-      length = Risc.syscall_reg(2).set_compiler(compiler)
+      word = Risc.syscall_reg(2).set_compiler(compiler)
+      length = Risc.syscall_reg(3).set_compiler(compiler)
       builder.build do
         string = message[:receiver].to_reg.known_type(:Word)
         integer << string[:char_length]