Extend module level efferent coupling test cases.

Author: Barnabás Domozi

plugins/cpp_metrics/test/sources/parser/module_c/c2.h

@@ -2,11 +2,13 @@
 #define CC_CPP_MODULE_METRICS_TEST_C2
 
 #include "../module_a/a2.h"
+#include "../module_b/b1.h"
 
 namespace CC_CPP_MODULE_METRICS_TEST
 {
 class C2 {
   A2 a2;
+  B1 b1;
 };
 }