RFC: remove <sys/sysmacros.h> from <sys/types.h>

[Zack Weinberg]

On Fri, Nov 13, 2015 at 9:21 AM, Zack Weinberg <zackw@panix.com> wrote:
> sys/sysmacros.h defines three macros - major, minor, makedev - that
> are likely to collide with user symbols.  That would be fine, since
> it's off by itself, but sys/types.h includes sys/sysmacros.h under
> __USE_BSD, which means anyone who defines _BSD_SOURCE or _GNU_SOURCE
> and includes sys/types.h gets the macros.

Note: as far as I can tell sys/types.h is the only glibc-installed
header that directly includes sys/sysmacros.h.