Eliminate TSan warnings for print_proc variables assignment (gctest)

Eliminate TSan warnings for print_proc variables assignment (gctest)

Now GC_is_valid_displacement_print_proc and GC_is_visible_print_proc
are set only once (before the first invocation of run_one_test).

* tests/test.c [DBG_HDRS_ALL] (set_print_procs): New macro (defined
to (void)0).
* tests/test.c [!DBG_HDRS_ALL] (set_print_procs): New function (which
sets GC_is_valid_displacement_print_proc and GC_is_visible_print_proc).
* tests/test.c (fail_count, fail_proc1, TEST_FAIL_COUNT): Do not
define if DBG_HDRS_ALL.
* tests/test.c [!DBG_HDRS_ALL] (run_one_test): Do not set
GC_is_valid_displacement_print_proc and GC_is_visible_print_proc.
* tests/test.c (main): Call set_print_procs() before run_one_test().
* tests/test.c [PCR] (test): Likewise.