query on system.h include order check

[Pádraig Brady]

The commit message here doesn't explain why this was done:
http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=SH-UTILS-2_0_12-112-g13221a5

Why not just include <sys/types.h> in system.h?

Would this be better served these days with a syntax-check?

Note I introduced a typo in the last change to this macro in 2011
which effectively avoided this check entirely
(notice the triple underscore in
http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=v8.9-10-ge1aaf89)
So should we just remove this check?

cheers,
Pádraig.