Fix for a race in BGSAVE that may result in some data not being saved as soon as possible (when the configured saving triggers should fire). Also known as Issue 313, more details there in the google code issue.

Fixed segfault in freeMemoryIfNeeded due to the fact that keys are now sds strings and not objects in the main hash table, thanks to Anthony Lauzon for spotting the bug and providing a patch.

redis-cli tests commented out since there is a problem with the CI server and this tests, will be activated again once the problem is fixed

Issue 179 fixed, now redis-cli is able to parse correctly multi bulk replies with elements that are errors

The pid file is now created only after the server is correctly initialied. It is also removed on sigterm and when the stack trace is produced after a sigbus or a sigsegv. This two changes should fix the Issue 175

slave with attached slaves now close the conection to all the slaves when the connection to the master is lost. Now a slave without a connected link to the master will refuse SYNC from other slaves. Enhanced the replication error reporting. All this will fix Issue 156