Change the cpp test to be optional

Remove unnecessary defines from the test.
Test by defining TEST_CPP using makefiles or cmake.
diff --git a/programs/Makefile b/programs/Makefile
index c5dd9f9..844d680 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -70,7 +70,6 @@
 	test/ssl_cert_test$(EXEXT)	test/benchmark$(EXEXT)		\
 	test/selftest$(EXEXT)		test/udp_proxy$(EXEXT)		\
 	test/zeroize$(EXEXT)						\
-	test/header_test$(EXEXT)								\
 	util/pem2der$(EXEXT)		util/strerror$(EXEXT)		\
 	x509/cert_app$(EXEXT)		x509/crl_app$(EXEXT)		\
 	x509/cert_req$(EXEXT)		x509/cert_write$(EXEXT)		\
@@ -80,6 +79,10 @@
 APPS +=	ssl/ssl_pthread_server$(EXEXT)
 endif
 
+ifdef TEST_CPP
+APPS += test/header_test$(EXEXT)
+endif
+
 .SILENT:
 
 .PHONY: all clean list