Security: Cross Protocol Scripting protection.

This is an attempt at mitigating problems due to cross protocol
scripting, an attack targeting services using line oriented protocols
like Redis that can accept HTTP requests as valid protocol, by
discarding the invalid parts and accepting the payloads sent, for
example, via a POST request.

For this to be effective, when we detect POST and Host: and terminate
the connection asynchronously, the networking code was modified in order
to never process further input. It was later verified that in a
pipelined request containing a POST command, the successive commands are
not executed.
int dictSdsKeyCaseCompare(void *privdata, const void *key1,
        const void *key2)
{
    DICT_NOTUSED(privdata);

    return strcasecmp(key1, key2) == 0;
}

int dictSdsKeyCaseCompare(void *privdata, const void *key1,
        const void *key2)
{
    DICT_NOTUSED(privdata);

    return strcasecmp(key1, key2) == 0;
}
