added Boolean_concept to concept checks to tighten up LessThanComparable

(thanks to Brian McNamara and Yassin Smaragdakis for catching this!)


[SVN r7902]

libs/concept_check

@@ -1 +1 @@
-Subproject commit cb61d684421ead9ca89107c5e790c62cc31001f1
+Subproject commit d9cb7a1e91b72c01dfc2183340f9fa06d2284ef0