Added needed const qualifier on out of line deffinition.

[SVN r19306]

include/boost/regex/v4/iterator_category.hpp

@@ -82,7 +82,7 @@ public:
 
 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
 template <class I>
-bool is_random_access_iterator<I>::value;
+const bool is_random_access_iterator<I>::value;
 #endif
 
 }