Fixes for IPv6, a date/time search bug, and a null modification list.  Includes hg/default branch.

Fixes for IPv6, a date/time search bug, and a null modification list.  Includes hg/default branch.

This is copied from the pending bitbucket pull-request prior to the github migration:
https://bitbucket.org/jbcheng/ossec-wui/pull-request/1/enable-ipv6-agents-fix-null-mod-list-add
It also includes the last two commits in the original bitbucket repository but apparently these ended up in the hg/default branch on github during the migration.

lib/os_lib_syscheck.php

  - Enabled IPv6 agents and filenames.

  - Fixed a bug in handling a null modification list.

site/search.php, site/searchfw.php, site/syscheck.php

  - Added ':' to search patterns for IPv6 addresses.

lib/os_lib_alerts.php

  - Fix a search bug that would skip the last alert log if the
    user specifies 'From' and 'To' times on different days and the time
    difference is less than 24 hours.

  - Enabled IPv6 source IP addresses.