[import] initial import of upstream latest master
Squashed 'mer-libsignon-glib/' content from commit 1ef44b5

git-subtree-dir: mer-libsignon-glib
git-subtree-split: 1ef44b5d9850787eb59e22fa8d8975d27be7791d
Merge commit '56de8ca6e6ed030a52034757a624f3a2d42d7fe9' as 'mer-libsignon-glib'
Initial import of packaging from Mer
modify packaging to work with subtree builds
Add missing build dependency on libtool
Remove direct dependencies on pkgconfig(signond)

Mer provides this in the wrong package (not our one) so we need to work around
this.
Requires is not BuildRequires
[libsignon-glib] Patch out docs build.