Bug#47896: MS_SYNC Macros Missing from Hurd development environment

[Brent Fulgham <brent.fulgham@xpsystems.com>]

Package: libc0.2-dev
Version: 2.1.2-0pre12

I was starting to work on apt support on the Hurd.

Apt makes use of the msync function, which I see is
supported in the Hurd (according to the sys/mman.h 
file).

When I attempt to compile, however, I get complaints
about the use of MS_SYNC (undefined).

Sure enough, the sys/mman.h doesn't define this, and
neither does bits/mman.h.

On Linux, the various flag values for msync are defined
in /usr/include/asm/mman.h.  We don't seem to have
anything similar (except perhaps bits/mman.h) unless
I have forgotten to reinstall some development package.

Should the MS_* macros be included in bits/mman.h?  It
seems like other things (found in /usr/include/asm/mman.h
on Linux) are defined here.

Here are the definitions (under Linux):
#define MS_ASYNC        1               /* sync memory asynchronously */
#define MS_INVALIDATE   2               /* invalidate the caches */
#define MS_SYNC         4               /* synchronous memory sync */

Thanks,

-Brent