change logging defaults

I propose to change some defaults:

log_autovacuum_min_duration = 0
log_checkpoints = on
log_lock_waits = on (and log_recovery_conflict_waits too?)
log_temp_files = 128kB

Note that pg_regress does this:
| fputs("\n# Configuration added by pg_regress\n\n", pg_conf);
| fputs("log_autovacuum_min_duration = 0\n", pg_conf);
| fputs("log_checkpoints = on\n", pg_conf);
| fputs("log_line_prefix = '%m %b[%p] %q%a '\n", pg_conf);
| fputs("log_lock_waits = on\n", pg_conf);
| fputs("log_temp_files = 128kB\n", pg_conf);
| fputs("max_prepared_transactions = 2\n", pg_conf);

-- 
Justin