CPP: Add test cases involving __builtin_complex.

Author: geoffw0

cpp/ql/test/query-tests/jsf/4.13 Functions/AV Rule 114/complex.c

@@ -0,0 +1,16 @@
+
+/*_Complex double complexTest1(float a, float b) {
+	_Complex double x = __builtin_complex(a, b); // BAD [EXTRACTOR ERROR]
+}
+
+_Complex double complexTest2(float a, float b) {
+	auto x = __builtin_complex(a, b) * 2.0f; // BAD [EXTRACTOR ERROR]
+}
+
+_Complex double complexTest3(float a, float b) {
+	return __builtin_complex(a, b); // GOOD [EXTRACTOR ERROR]
+}
+
+auto complexTest4(float a, float b) {
+	return __builtin_complex(a, b) * 2.0f; // GOOD [EXTRACTOR ERROR]
+}*/