Fix build on macos 10.13 (High Sierra).

Inequality comparisons between pointers and integers are no longer allowed.

Has this been sent upstream?

@ben.boeckel No. The GDAL 1.x branch does not appear to be maintained (no release in over a year; many 2.x releases).

sigh At some point we'll have to bite that bullet…

+1

Do: merge

mentioned in commit 318c0914

merged