Rename tag emplace to in_place

To conform to N3672.
Function emplace now returns void

To conform to N3672.
Remove namespace experimental

To conform to N3672.
cmake support from Jason Toffaletti
gcc 4.8 has is_trivially_destructible; others do not
silence no-return warnings
update test_optional for name and namespace changes
Merge branch 'n3672'
Remove constexpr from && version of value_or()

As per 20.5.4.5 of N3672, the && version of value_or() is not constexpr.
Enable rvalue references for *this in GCC 4.8.1+
Fix moved_on_value_or test

Change std::emplace to std::in_place