Add CI framework

- travis with valgrind, cppcheck, ubsan, codecov, covscan (future)
  - appveyor with MSVC 2010 through 2017, cygwin 32/64, mingw 32/64
  - README, LICENSE, etc.

include/boost/concept_check.hpp

@@ -734,8 +734,8 @@ namespace boost
    private:
       void const_constraints(const C& cc)
       {
-          const_reverse_iterator i = cc.rbegin();
-          i = cc.rend();
+          const_reverse_iterator _i = cc.rbegin();
+          _i = cc.rend();
       }
       C c;
   };