[Bug-gcal] Error regarding gnulib fseeko.c when building latest version

[Doron Behar]

Hello gcal developers,

I think the gnulib version bundled with gcal on the latest release is
outdated. I'm getting the following error when trying to compile it on
Arch Linux:

```
  CC       fseeko.o
fseeko.c: In function 'rpl_fseeko':
fseeko.c:110:4: error: #error "Please port gnulib fseeko.c to your platform! 
Look at the code in fseeko.c, then report this to bug-gnulib."
   #error "Please port gnulib fseeko.c to your platform! Look at the code in 
fseeko.c, then report this to bug-gnulib."
    ^~~~~
make[4]: *** [Makefile:1852: fseeko.o] Error 1
```

I've [asked for advice on the Arch Linux forums][1] and I received the
suggestion to report this problem upstream although there seems to be a
[patch used in fedora][2] which I thought you may want to know.

[1]: https://bbs.archlinux.org/viewtopic.php?pid=1808289
[2]: 
https://src.fedoraproject.org/rpms/gcal/blob/master/f/gcal-glibc-no-libio.patch