Using ImagePNG in CAPTCHA helper
Using ImagePNG function, if ImageJPG not exists
Merge pull request #3173 from ET-NiK/develop

Using ImagePNG in CAPTCHA helper
Polish changes following PR #3173
CSRF whitelist supports regex

Signed-off-by: Casey Hancock <crh431@gmail.com>
Cache_redis: Adding serialization support.
Skip CI_Encrypt tests if MCrypt is not available

Rel: #3185
Fix #3187
Cache_redis: AND -> && correction, srrict in_array() check.
Cache_redis: Strinct array_search() for now.
Cache_redis, delete() method: Removing code for updating the internal cache, it is useless.
Cache_redis, Hardcoded name for the auxilary Redis set - '_ci_redis_serialized'.
Cache_redis, delete() method: Bringing back a line of code.
Cache_redis, delete() method: Try to remove a key from Redis auxilary set only when the corresponding value is really deleted.
Alter Pull #3176 to follow discussion
Alter Pull #3176 - CSRF Whitelist
Merge pull request #3176 from caseyh/develop

CSRF whitelist supports regex
[ci skip] Polish changes from PR #3176
Cache_redis, save() method: An optimization, moving sRemove call.
Cache_redis: Refactoring if delete() method.
Cache_redis: Polishing.