Header definition changes for clang

[mbartle]

When running make check, clang is much fussier about the order of header includes than gcc is. It complains about the use of operator<< in scope/test when both scope/test.h and pair_out.h are included in a couple of test source files. It discovers the use of pair_out.h's operator<< in the test's use of a scope/test function, but scope/test is included before pair_out.h, so it complains that that definition of operator<< is in the wrong place. It seems to be in the family of issues detailed at http://clang.llvm.org/compatibility.html#dep_lookup.

Also, in one file, a std::vector was used without #include <vector>. I don't know how gcc was compiling that.