r26255: Work around another broken aspect of sys/capability.h on RHEL5.

r26255: Work around another broken aspect of sys/capability.h on RHEL5.

This is synced from samba3 v3-2-test/11bcdf780e164659b89:

The /usr/include/sys/capability.h defines _LINUX_TYPES_H
which prevents /usr/include/linux/types.h from being parsed
(when included afterwards). Thus certain types are undefined
that are for instance needed in /usr/include/linux/dqblk_xfs.h.
This breaks the build of lib/sysquotas_xfs.c in Samba3.

This commit adds a configure check and a workaround for this.

Michael
(This used to be commit df3e151992f0b942554034dd143ab8d7f0d7a75b)