C++: Specify GNU version on min/max test

The `<?` and `>?` operators where removed in g++ in version 4.3, and the
latest version of our our frontend enforces this through a version check.
Hence, to keep the test working, we not to explicitly specify a version.

cpp/ql/test/library-tests/exprs/min_max/expr.expected

@@ -1,6 +1,6 @@
-| test.cpp:3:13:3:13 | i |
-| test.cpp:3:13:3:18 | ... <? ... |
-| test.cpp:3:18:3:18 | j |
 | test.cpp:4:13:4:13 | i |
-| test.cpp:4:13:4:18 | ... >? ... |
+| test.cpp:4:13:4:18 | ... <? ... |
 | test.cpp:4:18:4:18 | j |
+| test.cpp:5:13:5:13 | i |
+| test.cpp:5:13:5:18 | ... >? ... |
+| test.cpp:5:18:5:18 | j |

cpp/ql/test/library-tests/exprs/min_max/test.cpp

@@ -1,3 +1,4 @@
+// semmle-extractor-options: --gnu_version 40200
 
 void f(int i, int j) {
     int k = i <? j;