print/scribus-devel: fix on GCC architectures, change maintainer, add USES=gnome

Add USES=compiler:c++11-lang.

Remove ifdef FreeBSD from isnan check.

Change maintainer to pkubaj@freebsd.org from my old address.

Add USES=gnome.

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D20048