C++: Add more deduction guide tests

Author: jketema

cpp/ql/test/library-tests/deduction_guides/missing_template_class.expected

@@ -0,0 +1,5 @@
+import cpp
+
+from DeductionGuide d
+where not exists(d.getTemplateClass())
+select d

cpp/ql/test/library-tests/deduction_guides/missing_template_class.ql

@@ -0,0 +1,5 @@
+| file://:0:0:0:0 | C | test.cpp:4:8:4:8 | C<T> |
+| file://:0:0:0:0 | C | test.cpp:4:8:4:8 | C<T> |
+| test.cpp:5:5:5:5 | (unnamed deduction guide) | test.cpp:4:8:4:8 | C<T> |
+| test.cpp:6:5:6:5 | (unnamed deduction guide) | test.cpp:4:8:4:8 | C<T> |
+| test.cpp:12:1:12:1 | C | test.cpp:4:8:4:8 | C<T> |

cpp/ql/test/library-tests/deduction_guides/template_class.expected

@@ -3,13 +3,16 @@
 template<typename T>
 struct C {
     C(const T);
+    C(char, char);
 };
 
 C(const double)  -> C<int>;
 
 template<typename T>
 C(const T)  -> C<int>;
 
+C(char, char) -> C<char>;
+
 void test() {
     new C<char>(0);
     new C<int>(0);