add missing hasOneof method to check presence of oneof fields

[anight]

Possible solution for #8001 and #7961

test.proto:

syntax = "proto3";
package Test;
message Test {
        oneof O {
                int32 A = 1;
                int32 B = 2;
        }
}

test.php:

<?php
        dl('protobuf.so');
        require_once './vendor/autoload.php';
        $t = new Test\Test();
        print_r($t->hasB() === false);
?>

Output:

$ php ./test.php
Fatal error: Uncaught Error: Call to undefined method Test\Test::hasOneof() ...

Expected output:

$ php ./test.php
1

[haberman]

This is great, thanks! Just a few small comments.

[haberman]

Can you add a test for this?

[haberman]

Test looks great, but it might be better to move it into one of the existing test files (I think GeneratedClassTest.php would be a good option). Adding new files is a bit more involved because then the new file has to get added to the Makefile:

https://github.com/protocolbuffers/protobuf/blob/master/Makefile.am#L767-L961

[haberman]

I kicked off the tests. If you move your new test into an existing file, it should fix the "distcheck" test failure.

[haberman]

We'd like to cut a branch for our upcoming release today and this fix should definitely go in. Are you planning to push again in the next few hours? If not I may need to adopt this change in a different PR to get it merged.

[haberman]

Actually let me merge this now and the send a follow-up PR to fix the test failures.