added goto

tests/goto.expected

@@ -0,0 +1,3 @@
+3
+2
+1

tests/goto.sl

@@ -0,0 +1,12 @@
+import stdlib/stdlib.sl
+import stdlib/io.sl
+
+word main
+    3
+    label loop
+    dup puti cr
+    1 -
+    dup 0 >
+    if goto loop end
+    drop
+end

tests/goto.test

@@ -0,0 +1 @@
+python main.py tests/goto.sl -o /tmp/goto > /dev/null && /tmp/goto