Improved flow analysis in general and especially for "for" loops. Added more

tests.

test/misc/flow-while-01.c

@@ -63,8 +63,18 @@ static int f6(void)
     return a;
 }
 
-int main(void)
+static int f7(void)
 {
-    return f1() + f2() + f3() + f4() + f5() + f6();
+    while (a) {
+        return a;
+    }
+    /* Reachable */
+    a = 2;
+    return a;
+}
+
+int main(void)
+{
+    return f1() + f2() + f3() + f4() + f5() + f6() + f7();
 }