adds test for routine yac_abort

tests/mci/test_abort_c.c

@@ -8,6 +8,7 @@
 #include <mpi.h>
 #include "tests.h"
 #include "yac.h"
+#include "yac_core.h"
 
 static void custom_error_handler(
   MPI_Comm comm, const char * msg, const char * source, int line);
@@ -41,6 +42,8 @@ int main (void) {
 
   yac_set_abort_handler((yac_abort_func)custom_error_handler);
 
+  yac_abort(ref_comm_world, ref_msg, ref_source, ref_line);
+
   yac_abort_message(ref_msg, ref_source, ref_line);
 
   // test should never reach this point