misc/xiphos: Unbreak build

• Unbreak build by adding "-ftemplate-depth=1024" to CXXFLAGS
• Add missing libraries

While I'm here:

• Fix license and add path to license file
• Add "gnome" to USES because using USE_GNOME alone is deprecated
• Pet portlint

PR: 232997
Submitted by: Walter Schwarzenfeld <w.schwarzenfeld@utanet.at>
Reviewed by: tcberner (mentor)
Approved by: miwi (mentor)
Differential Revision: https://reviews.freebsd.org/D19210