Small fixes (PR #3022)

- Fix incorrect variable in mb_strlen() compat
- Micro-optimization of array_replace(), array_replace_recursive() compat
Merge branch 'develop' of github.com:EllisLab/CodeIgniter into develop
Added `_trans_failure` property to fix PHP Warning.
Fix docblock of URI->rsegments property
Merge pull request #3028 from vlakoff/phpdoc

Fix docblock of URI->rsegments property
Optimization in CI_URI::_set_uri_string()
Merge pull request #3027 from abdmaster/fix/db_transaction_failure

Added `_trans_failure` property to fix PHP Warning.
PHPUnit, what's wrong with you?
Fix a typo
xss_clean is not protecting GET requests that &item=/startwithslash

/webacd.do?isurlact=true&entactname=/webacd.do
becomes
/webacd.do?isurlact=true&entactname;=/webacd.do

This commit adds / to the regex to it will escape those GET requests

related to issue #3030
Merge pull request #3037 from DevelopmentDocumentopia/xss_clean_patch

xss_clean is not protecting GET requests that &item=/startwithslash
Account for PHP 5.6 changes related to charsets
Remove error-masking '@' in mysqli_driver (See: https://github.com/EllisLab/CodeIgniter/issues/3036)
Added support to Symbian OS platforms to recognize Nokia devices
Prepare image url.
Merge pull request #3040 from adrianorsouza/platform_support

Added support for Symbian OS platforms to recognize Nokia devices
Removed empty line.
[ci skip] Update a comment for CI_Input::input_stream()
Removed empty line
Merge pull request #3041 from egig/develop

Prepare image url.