Change name didn't work if reset initialization it's true

If user initializes the upload library with the reset flag as true, the
uploaded file doesn't change it's name, it's neccesary to initialize or
change the $_file_name_override every time.
Merge pull request #3169 from Patroklo/develop

Change name didn't work if reset initialization it's true
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