Minimal test for map/vector emplace memfuns

Upstream usage identified that GCC prior to 4.8 does not implement
the emplace member functions for maps.

Add a minimal test of presence and functionality of std::map::emplace.
Add a minimal test of presence and functionality of
std::vector::emplace.

These should cover the basic sequential and associative containers.
Use correct pair type order in map::emplace test

Tests on Mac identified that the incorrect type order is used
in the pair type for testing returns from maps's emplace member
function.

Use correct ordering as defined in the Standard, and update tests
of returned pair to check correct entries.