vbox: add vbox 5.1 C API header file.
vbox: add vbox 5.1 C API header file.

extracted from VirutalBox SDK and reindented with cppi.

libvirt/libvirt,libvirt/libvirt,nertpinx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,andreabolognani/libvirt,crobinso/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jardasgit/libvirt,datto/libvirt,jfehlig/libvirt,eskultety/libvirt,nertpinx/libvirt,olafhering/libvirt,olafhering/libvirt,jardasgit/libvirt,taget/libvirt,zippy2/libvirt,fabianfreyer/libvirt,eskultety/libvirt,taget/libvirt,datto/libvirt,eskultety/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,nertpinx/libvirt,andreabolognani/libvirt,crobinso/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,taget/libvirt,zippy2/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,taget/libvirt,taget/libvirt,zippy2/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,datto/libvirt,jfehlig/libvirt,olafhering/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,datto/libvirt,zippy2/libvirt,VenkatDatta/libvirt,crobinso/libvirt,olafhering/libvirt,andreabolognani/libvirt,datto/libvirt,nertpinx/libvirt,crobinso/libvirt,andreabolognani/libvirt,eskultety/libvirt,libvirt/libvirt