Used signbit instead of std::signbit function.
Used the "using namespace std" trick to get signbit working on multiple systems.
Plagiarized @atnnn's fix for sorted_datum_stream_t to get GCC 4.4.3 working.
Merge branch 'sam_1444' of github.com:rethinkdb/rethinkdb into sam_1444
Merge branch 'next' into sam_1444
Merge branch 'sam_1444' into next