fix make_pair future-proofing

let the compiler decide the correct make_pair template parameters - this would break in c++11 for lvalue / rvalue subtleties

see:

<http://stackoverflow.com/questions/9641960/c11-make-pair-with-specified-template-parameters-doesnt-compile>

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>