Fixes #5768: When setting `data-confirm` attribute to a submit button, clicking on the button would not trigger form submission

Improved checks where substr_compare is used, replaced more substr + comapre cases with substr_compare

fixes #4470

LOG_SYSLOG - messages generated internally by syslogd. As we know PHP is not a part of syslogd therefore we should use LOG_USER. (additionaly LOG_USER is the only valid log type under Windows operating systems)

fixes #4123

works on windows out of the box now.
fixes #3989

fixes issue #3989

Fixes #4071: `mail` component renamed to `mailer`, `yii\log\EmailTarget::$mail` renamed to `yii\log\EmailTarget::$mailer`

Fixes #3101: Improved handling of log target failures. It will now skip target and log reason instead of going into infinite cycle

fixes #2988

fixes #3245, #3244

Adjustments code according to the standards.
Adding missing PHPDoc comment.

fixes #2894

fixes #2894

fixes #2894