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

tests.

test/misc/flow-for-01.c

@@ -0,0 +1,90 @@
+int a;
+
+static int f1(void)
+{
+    for (;;) {
+        ++a;
+    }
+    /* Unreachable */
+    a = 2;
+    return a;
+}
+
+static int f2(void)
+{
+    for (;1;) {
+        ++a;
+    }
+    /* Unreachable */
+    a = 2;
+    return a;							 
+}
+
+static int f3(void)
+{
+    for (;;) {
+        ++a;
+        if (a == 5) break;
+    }
+    /* Reachable */
+    a = 2;
+    return a;
+}
+
+static int f4(void)
+{
+    for (;;) {
+        ++a;
+        return a;
+    }
+    /* Unreachable */
+    a = 2;
+}
+
+static int f5(void)
+{
+    for (;0;) {
+        /* Unreachable */
+        ++a;
+        return a;
+    }
+    /* Reachable */
+    a = 2;
+    return 0;
+}
+
+static int f6(void)
+{
+    for (;;) {
+        ++a;
+        if (a == 4) goto L;
+        return a;
+    }
+    /* Reachable via L */
+L:  a = 2;
+}
+
+static int f7(void)
+{
+    for (;0;) {
+        /* Unreachable but no warning */
+    }
+    a = 2;
+    return a;
+}
+
+static int f8(void)
+{
+    for (;a;) {
+        return a;
+    }
+    /* Reachable */
+    a = 2;
+    return a;
+}
+
+int main(void)
+{
+    return f1() + f2() + f3() + f4() + f5() + f6() + f7() + f8();
+}
+