C++: Add false positive testcase involving conversions.

Author: MathiasVP

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/IncorrectAllocationErrorHandling.expected

@@ -16,3 +16,4 @@
 | test.cpp:151:9:151:24 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:152:15:152:18 | { ... } | This catch block |
 | test.cpp:199:15:199:35 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:201:16:201:19 | { ... } | This catch block |
 | test.cpp:212:14:212:34 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:213:34:213:36 | { ... } | This catch block |
+| test.cpp:225:23:225:29 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:226:34:226:36 | { ... } | This catch block |

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/test.cpp

@@ -218,4 +218,10 @@ void good_new_catch_exception_in_assignment() {
   try {
     p = new int; // GOOD
   } catch(const std::bad_alloc&) { }
+}
+
+void good_new_catch_exception_in_conversion() {
+  try {
+    long* p = (long*) new int; // GOOD [FALSE POSITIVE]
+  } catch(const std::bad_alloc&) { }
 }