Bump ebuilds to 3.1.6 (server only)

- use autotools-utils
- useflags optimizations
- patches for libsearpc and ccnet
- add amd64 platform

libsearpc ebuild is kind of a weird hack - upstream says one should use
the tag v3.0-latest, but I fear that this tag is not always one the same
commit, hence the name "latest". Because of this I chose the current
commit hash of the tag as the SRC_URI.

Patches and some from several ArchLinux AUR packages:
https://aur.archlinux.org/packages/libsearpc
https://aur.archlinux.org/packages/ccnet
https://aur.archlinux.org/packages/seafile-server
Add seafile-server-3.1.6 ebuild
Use python-single-r1 eclass
Add elog and ewarn messages to seafile-server
Merge pull request #7 from Strayer/bump-to-3.1.6

Bump to 3.1.6, add seafile-server ebuild