How to deal with inline asm functions in Phobos/druntime?

[Johan Engelen via digitalmars-d-ldc]

I wrote a non-asm ilogb, that actually runs quite a bit faster 
than what DMD or LDC do standard, and should also be much more 
portable.
See
https://github.com/D-Programming-Language/phobos/pull/3186