Add testcase from issue 602

cpp_thread_test/Makefile

@@ -1,6 +1,6 @@
 include ../Makefile.rule
 
-all :: dgemv_tester dgemm_tester
+all :: dgemv_tester dgemm_tester test_dgemm_omp
 
 dgemv_tester :
 	$(CXX) $(COMMON_OPT) -Wall -Wextra -Wshadow -fopenmp -std=c++11 dgemv_thread_safety.cpp ../libopenblas.a -lpthread -o dgemv_tester
@@ -10,5 +10,8 @@ dgemm_tester : dgemv_tester
 	$(CXX) $(COMMON_OPT) -Wall -Wextra -Wshadow -fopenmp -std=c++11 dgemm_thread_safety.cpp ../libopenblas.a -lpthread -o dgemm_tester
 	./dgemm_tester
 
+test_dgemm_omp:
+	$(CC) $(COMMON_OPT) -Wall -Wextra -Wshadow -fopenmp test_dgemm_omp.c ../libopenblas.a -lpthread -o test_dgemm_omp
+	
 clean ::
 	rm -f dgemv_tester dgemm_tester