Convert configuration-related cpp conditional logic to use static
constant variables, e.g.:
#ifdef JEMALLOC_DEBUG
[...]
#endif
becomes:
if (config_debug) {
[...]
}
The advantage is clearer, more concise code. The main disadvantage is
that data structures no longer have conditionally defined fields, so
they pay the cost of all fields regardless of whether they are used. In
practice, this is only a minor concern; config_stats will go away in an
upcoming change, and config_prof is the only other major feature that
depends on more than a few special-purpose fields.
Fix the logic in stats_print() such that if the "a" flag is passed in
without the "m" flag, merged statistics will be printed even if only one
arena is initialized.
