Improvements in syscheck realtime monitoring

[vikman90]

Related issue: #431

• Upgrade checksum hash table for every reported file (not only the first time)
• Internal option syscheck.rt_delay to tune the delay before attending an RT notification. The default configuration decreases the delay from 1 second to 10 milliseconds
• Granularize syscheck RT process from 5 minutes to 1 second. This will make the frequency option more accurate.
• Allow to speed up the startup time: formula changed from tsleep + 10 to tsleep * 5. The actual delay will remain for the default configuration, but this formula allows to null the time if syscheck.sleep is set to 0 in the internal options.