This patch moves more includes (most of them, to tell the truth) to
common/include directory. This completes the list of includes needed
to compile current trunk with the new libc (but to do that you need
more patches in queue).
This patch also contains some modification (for compilation with new
headers) to the common includes under __NBSD_LIBC, the define used
in mk script to specialize compilation with new includes.
Headers that will be shared between old includes and NetBSD-like includes
are moved into common/include tree. They are still copied in /usr/include
in 'make includes', so compilation and programs aren't be affected.
