Fix User Guide Search button issue

Signed-off-by: Hashem Qolami <hashem@qolami.com>
Update user_agents.php

Added Win 8.1 user agent to the array
Added post-increment for $count

It has been added the missing post-increment for variable $count.
Cleanup DB_forge _process_indexes
Cleanup DB_forge _process_indexes
Merge pull request #2777 from mjnaderi/develop

Cleanup DB_forge _process_indexes
Use table name as a prefix for index names
Merge pull request #2779 from mjnaderi/develop

Use table name as a prefix for index names
[ci skip] Add notes to get_compiled_insert(), get_compiled_update() docs
[ci skip] Fix a changelog message
EXISTS / NOT EXISTS clause support for  DB_query_builder.
EXISTS / NOT EXISTS clause support for  DB_driver
EXISTS / NOT EXISTS clause support for  DB_driver
changed EXISTS / NOT EXISTS pattern
@narfbg "It has parenthesis, so use the IN / NOT IN pattern as a base."
added changelog about EXISTS / NOT EXISTS
@narfbg "And you should also add a changelog entry for this addition. :)"
so we need \sNOT EXISTS
Merge pull request #2781 from tufanbarisyildirim/develop

EXISTS / NOT EXISTS clause support for  DB_driver
Polishing changes from #PR #2781

Looks like an unnecessary commit was made by the author just as I was clicking the Merge button. :)
Remove unneeded manual escaping of session data
Remove _serialize() and _unserialize() methods

Since removing the unneeded manual escaping code, there is no-longer any reason
to have the serialization functions abstracted. This also allows us to only
suppress errors when unserializing cookie data, and only trim when we are
unserializing database data (see commit 6b8312).