Re: [boost] A few more critical dependencies

Rene Rivera wrote:

Although I would gladly accept a move of boost/detail/endian.hpp to Predef (since I'm the sole author at this point). A much nicer solution would be to change boost/mpl/string.hpp to use the non-detail endian macros of Predef. As ti gets us closer to removing detail/endian.hpp entirely.

I've changed mpl/string.hpp to use Predef directly, but I still think that we should move detail/endian.hpp to Predef, as this is where it rightfully belongs.