prepare for upcoming liblognorm 1.0.0 release

The new liblognorm relase has an incompatible API, so
we cannot use it to compile this version of rsyslog.
doc: remove some implementation details
Merge branch 'v7-stable' into v7-devel
bugfix: mmrfc5424addhmac: "key" parameter was not properly processed
Merge branch 'c10' into v7-devel

Conflicts:
	configure.ac