synchronous I/O networking functions originally used just for replication refactored in a file as generally useful, they are used in the cluster branch for MIGRATE.

Also, use tcmalloc functions explicitly via macros to prevent symbol
lookups to resolve to native malloc/free on OSX.

Make sure to reset the signal handler and deliver again the original crashing signal when dumping the stack trace. This will allow to dump the core if core dumping is enabled.

prevent small integer sharing when maxmemory is active. So every object will use a private LRU field and the LRU algorithm can work well

Don't increment dirty on expireIfNeeded() as natural expires are not considered database changes. This will avoid useless read-only commands in the AOF file as a result of, for instance, a GET operation triggering an expirIfNeeded() call resulting in an expired key removed.

Object approximated LRU algorithm enhanced / fixed / refactored. This is used for the VM currently but will soon be used for maxmemory expiring.

maxmemory fixed, we now try to release memory just before we check for the memory limit. Before fixing there was code between the attempt to free memory and the check for memory limits, and this code could result into allocations going again after the memory limit.

fixed an alignment problem with time_t is 32 bit, long is 64 bit, and arch is sparc or any other where unaligned accesses will result to sigbus

modified a bit addReply() to play better with copy on write now that we have a static buffer. Changed the name of a function from _ensureFileEvent() to _installWriteEvent().

This should fix Issue 332: when there is a background process saving we still allow the hash tables to grow, but only when a critical treshold is reached. Formerly we prevented the resize at all triggering pathological O(N) behavior. Also there is a fix for the statistics in INFO about the number of keys expired

Thanks to sylr@github
Signed-off-by: NPedro Melo <melo@simplicidade.org>

Signed-off-by: NPedro Melo <melo@simplicidade.org>