Validate AES-GCM Authentication Tag

fix canonicalization error

Removes BC breaking change

Add tab to list of whitespace values to remove from cert
loadKey should check return value for openssl_get_privatekey
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Support OAEP (from unreleased 3.1.1)

Add support for AES-GCM encryption
Minor improvements and bug fixes

Security Release for CVE-2019-3465

Security release

Add PHP 7.3 support

Backports changes from 3.0 branch.
This will be the last supported release from 2.x branch

Mainly security related release. See Changelog for more details