Doesn't build on 32 bit platforms

[clausecker]

When building packages depending on this one on 32 bit platforms, the following error occurs:

# github.com/pydio/cells/vendor/github.com/yvasiyarov/php_session_decoder/php_serialize
vendor/github.com/yvasiyarov/php_session_decoder/php_serialize/unserialize.go:266:19: UNSERIALIZABLE_OBJECT_MAX_LEN (un
typed int constant 10737418240) overflows int

Please fix this bug.