glcpp/tests: Add a test for #if defined (identifier)

Previously we only tested #if defined identifier (without parenthesis).

glcpp/tests/065-if-defined-parens.c

@@ -0,0 +1,17 @@
+#if defined(foo)
+failure_1
+#else
+success_1
+#endif
+#define foo
+#if defined ( foo )
+success_2
+#else
+failure_2
+#endif
+#undef foo
+#if defined (foo)
+failure_3
+#else
+success_3
+#endif

glcpp/tests/065-if-defined-parens.c.expected

@@ -0,0 +1,18 @@
+
+
+
+success_1
+
+
+
+success_2
+
+
+
+
+
+
+
+success_3
+
+