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/data/continue.c b/libacc/tests/data/continue.c
new file mode 100644
index 0000000..d8b8e36
--- /dev/null
+++ b/libacc/tests/data/continue.c
@@ -0,0 +1,13 @@
+int main() {
+    int i, j, sum;
+    sum = 0;
+    for (i = 0; i < 10; i++) {
+        if (i & 1) continue;
+        for (j = 0; j < 10; j++) {
+            if (j & 1) continue;
+            sum += i * j;
+        }
+    }
+    return sum;
+}
+
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")