Call GC_stats/verbose_log_printf instead of GC_log_printf if print_stats

Call GC_stats/verbose_log_printf instead of GC_log_printf if print_stats
(code refactoring)

* alloc.c (GC_try_to_collect_inner, GC_stopped_mark,
GC_finish_collection): Use GC_stats_log_printf instead of
GC_log_printf inside "if (GC_print_stats)" blocks.
* include/private/gc_priv.h (GC_COND_LOG_PRINTF): Likewise.
* finalize.c (GC_print_finalization_stats): Use GC_stats_log_printf
instead of GC_log_printf (since the function is invoked only inside
"if (GC_print_stats)" blocks).
* include/private/gc_priv.h (GC_printf, GC_log_printf): Refine
comment.
* include/private/gc_priv.h (GC_stats_log_printf,
GC_verbose_log_printf): New macro (redirected to GC_log_printf).
* reclaim.c (GC_reclaim_all): Use GC_verbose_log_printf instead of
GC_log_printf inside "if (GC_print_stats==VERBOSE)" blocks.
* include/private/gc_priv.h (GC_COND_LOG_PRINTF): Likewise.
* misc.c (GC_LOG_PRINTF_IMPL): New macro (only if GC_ANDROID_LOG,
copy most code from GC_log_printf).
* misc.c (GC_log_printf): Define separately for Android using
GC_LOG_PRINTF_IMPL macro (only if GC_ANDROID_LOG).