C++: Fix the suppression for alerts about enums

The suppression mechanism broke when I changed `relOpWithSwap` to take
fully-converted expressions as parameters.

Author: jbj

cpp/ql/src/Likely Bugs/Arithmetic/PointlessComparison.ql

@@ -38,7 +38,7 @@ where
   // a comparison between an enum and zero is always valid because whether
   // the underlying type of an enum is signed is compiler-dependent
   not exists (Expr e, ConstantZero z
-      | relOpWithSwap(cmp, e, z, _, _) and
+      | relOpWithSwap(cmp, e.getFullyConverted(), z, _, _) and
         e.getUnderlyingType() instanceof Enum) and
 
   // Construct a reason for the message. Something like: x >= 5 and 3 >= y.

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.c

@@ -207,7 +207,7 @@ enum my_enum {
 };
 
 int myFunction6(enum my_enum e) {
-	if (e < 0) { // BAD
+	if (e < 0) { // GOOD (suppressed because it's platform-dependent)
 		return 1;
 	}
 	return 0;

cpp/ql/test/query-tests/Likely Bugs/Arithmetic/PointlessComparison/PointlessComparison.expected

@@ -31,7 +31,6 @@
 | PointlessComparison.c:126:12:126:18 | ... >= ... | Comparison is always true because a >= 20. |
 | PointlessComparison.c:129:12:129:16 | ... > ... | Comparison is always false because a <= 3. |
 | PointlessComparison.c:197:7:197:11 | ... < ... | Comparison is always false because x >= 0. |
-| PointlessComparison.c:210:6:210:10 | ... < ... | Comparison is always false because e >= 0. |
 | PointlessComparison.c:264:12:264:22 | ... >= ... | Comparison is always true because dbl >= 0 and -0 >= - .... |
 | PointlessComparison.c:273:9:273:18 | ... > ... | Comparison is always false because c <= 0. |
 | PointlessComparison.c:283:13:283:19 | ... >= ... | Comparison is always true because c >= 11. |