C++: Add a test for cpp/empty-if (AI).

Author: geoffw0

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/FutileConditional/FutileConditional.cpp

@@ -0,0 +1,15 @@
+void emptyIfs(int value) {
+  if (value) {} // $ Alert
+
+  if (value > 1) {
+  } // $ Alert
+
+  if (value) {
+    ++value;
+  }
+
+  if (value) {
+  } else {
+    ++value;
+  }
+}

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/FutileConditional/FutileConditional.expected

@@ -0,0 +1,2 @@
+| FutileConditional.cpp:2:3:2:15 | if (...) ...  | If-statement with an empty then-branch and no else-branch. |
+| FutileConditional.cpp:4:3:5:3 | if (...) ...  | If-statement with an empty then-branch and no else-branch. |

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/FutileConditional/FutileConditional.qlref

@@ -0,0 +1,2 @@
+query: Likely Bugs/Likely Typos/FutileConditional.ql
+postprocess: utils/test/InlineExpectationsTestQuery.ql