Support waffle>1.7.4

Hello,

while lately discussion has mostly been about how to exclude waffle from
the non-Windows build, I would like to request an update in the other
direction. Last November, waffle-jna 1.7.5 was released, containing an
incompatible API change that is also present in all released 1.8
versions. The fix is simple; as far as the code goes, it is a one-line
patch. What incantations may be required on the Maven side, I do not know.

The API change was made as part of fixing a handle leak [1].

Applying this patch raises the minimum required waffle version to 1.7.5
or 1.8.0.

Thank you.

[1] <https://github.com/dblock/waffle/pull/239>

--
Christian