Adjust printf calls in gctest check_heap_stats so that each has new-line

Adjust printf calls in gctest check_heap_stats so that each has new-line

This is useful if GC_printf uses Android logging.

* tests/test.c (finalizable_count): Do not define if
GC_NO_FINALIZATION.
* tests/test.c (mktree): Do not increment finalizable_count if
GC_NO_FINALIZATION.
* tests/test.c (check_heap_stats): Do not print finalization counts
if GC_NO_FINALIZATION or GC_get_find_leak() is true; call GC_printf
to output finalization counts and the check result just once (i.e.
the whole line is printed in a single GC_printf call).
* tests/test.c [!NO_CLOCK] (check_heap_stats): Call GC_printf just
once to output "Completed <N> collections" together with the total
GC time value and the number of marker threads (i.e. the whole line
is printed in a single GC_printf call).