Add support for the continue statement

Add error check for a break statement that's not inside a loop. (We just
generated bad code before. Oops!)
diff --git a/libacc/tests/test.py b/libacc/tests/test.py
index 6e0899c..d93af46 100644
--- a/libacc/tests/test.py
+++ b/libacc/tests/test.py
@@ -187,6 +187,10 @@
         self.compileCheck(["-R", "data/returnval-ansi.c"],
         "Executing compiled code:\nresult: 42\n")
 
+    def testContinue(self):
+        self.compileCheck(["-R", "data/continue.c"],
+        "Executing compiled code:\nresult: 400\n")
+
     def testStringLiteralConcatenation(self):
         self.compileCheck(["-R", "data/testStringConcat.c"],
         "Executing compiled code:\nresult: 13\n", "Hello, world\n")