Reference the test case "packs" to fix warnings

Put the various atf_tc_pack_t variables generated by ATF_TC to use in
the macros_h_test.c file so that we prevent some build warnings (and
thus some build errors) with clang and -Wunused.

Obtained from:  atf (git 70126d013db25c72539803f19f7e00baddacdf51)