[tex-live] Source build breakage with system poppler-0.63

[Akira Kakuto]

> With last night's 2018-pre source (r47264) I got a new build failure
> with system poppler because my latest system has moved to using
> poppler-0.63.0.  It turns out that Jerry James (Cc:'d) fixed this for
> fedora rawhide's current 2017 build, but the changed code has moved a
> lot further down the file in 2018.

Thanks very much. Applied in r47281.

Best,
Akira