[libc++][patch] Add missing parts from <functional>

[Sebastian Redl]

On 27.07.2013, at 13:47, Sebastian Redl wrote:

> <functional> is missing minor things:
> - The synopsis comments does not contain any of the bit_* functors.

These were added in C++11, actually. Seems the synopsis didn't update that part from C++03.

> - The actual implementation of bit_not is missing.


And that's an oversight in C++11 that was corrected in N3421, so it's a C++14 feature. Might want to guard it.

Working on a full implementation of N3421 btw.

Sebastian