OUT/RulesParser: add !=~ operator

"Does not match regex" for convenience and symmetry

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
OUT/RulesParser: Parse/implement BooleanInfixOperatorProduction

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
OUT/RulesParser: add comment stating why Ephemerizable{In,Pre}fixOpProduction exists

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
OUT/RulesParser: fix broken copy-pasted error message

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>