bugfix: RainerScript: invalid ruleset names were accepted

...during ruleset defintion, but could of course not be used when
e.g. calling a ruleset.
IMPORTANT: this may cause existing configurations to error out on start,
as they invalid names could also be used e.g. when assigning rulesets.
warn on invalid ruleset name

but keep accepting it. This is a forward-compatibility change
so that users will not run into surprises when they apply 8.5.1.
Merge branch 'v7-stable' into v8-stable
Merge branch 'v8-stable'

Conflicts:
	runtime/ruleset.c