Slight adjustment in growth calculation.

INFO now contains the time (in usecs) needed to fork() in order to persist. The info is available in the stats section of INFO.

peak fragmentation ratio removed as it is a confusing field for users and trivial to compute at hand now that there is peak memory information in INFO output

save peak memory usage as statistic and show it in INFO. Also a new INFO field was added showing the fragmentation ratio using the peak memory info.

added minimal cluster section in INFO output. This is only useful to check if the instance is or not configured as a cluster node, all the other informations are accessible using the CLUSTER command.

DUMP implemented, RESTORE and MIGRATE fixed. Use zcalloc() instead of zmalloc()+memset() in sds.c when a new string is created with NULL initialization pointer.

centralized cluster config file name. Assigned slots in CLUSTER NODES output and in cluster config file.

propagate key eviction to slaves and AOF, like for expires, so that replicas and AOFs are always consistent even in maxmemory mode.

INFO commandstats section reset with config resetstat, a new microseconds per call field, and a few other minor things