Security: fix redis-cli buffer overflow.

Thanks to Fakhri Zulkifli for reporting it.

The fix switched to dynamic allocation, copying the final prompt in the
static buffer only at the end.
sds sdsCatColorizedLdbReply(sds o, char *s, size_t len) {
    char *color = "white";

    if (strstr(s,"<debug>")) color = "bold";
    if (strstr(s,"<redis>")) color = "green";
    if (strstr(s,"<reply>")) color = "cyan";
    if (strstr(s,"<error>")) color = "red";
    if (strstr(s,"<hint>")) color = "bold";
    if (strstr(s,"<value>") || strstr(s,"<retval>")) color = "magenta";
    if (len > 4 && isdigit(s[3])) {
        if (s[1] == '>') color = "yellow"; /* Current line. */
        else if (s[2] == '#') color = "bold"; /* Break point. */
    }
    return sdscatcolor(o,s,len,color);
}

sds sdsCatColorizedLdbReply(sds o, char *s, size_t len) {
    char *color = "white";

    if (strstr(s,"<debug>")) color = "bold";
    if (strstr(s,"<redis>")) color = "green";
    if (strstr(s,"<reply>")) color = "cyan";
    if (strstr(s,"<error>")) color = "red";
    if (strstr(s,"<hint>")) color = "bold";
    if (strstr(s,"<value>") || strstr(s,"<retval>")) color = "magenta";
    if (len > 4 && isdigit(s[3])) {
        if (s[1] == '>') color = "yellow"; /* Current line. */
        else if (s[2] == '#') color = "bold"; /* Break point. */
    }
    return sdscatcolor(o,s,len,color);
}
