manage large Kerberos tokens

[fralken]

This patch checks whether the returned Kerberos token, encoded in base64, fits the available buffer. If it is larger, the buffer is reallocated with the required dimension.
This patch was circulating for a few years and was recently proposed here by @bas524. I just cleaned it up a bit and made the reallocation conditional only when it is necessary to expand the buffer.

In the meantime, for the macos version, I replaced the deprecated gssapi apis with the GSS framework and removed some deprecated code.

[sonarqubecloud]

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[fralken]

@bas524 if you can test that this works for you we can merge this PR.

[sonarqubecloud]

Quality Gate passed

Kudos, no new issues were introduced!

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[jschwartzenberg]

I can at least confirm that Kerberos authentication works fine with this branch. I did not have issues in the past however.

[bas524]

@fralken, unfortunately I can't verify this PR, because I've changed my environment.

[fralken]

Thanks for the feedback @jschwartzenberg. It confirms that at least there are no regressions with this PR. I guess I can merge it.
No problem @bas524. Probably it is not very frequent to have a Kerberos configuration that generate large (more than 4kB in size) tokens.

[jschwartzenberg]

I can confirm that this solved Keberos issues for at least one user! @bas524 many thanks for figuring this out! @fralken great we could get it merged!