Simplify flags setup code

Instead of having two arrays, one for the flag values and another for
the flag names. Combine them both into a single array of structs which
hold both those bits of information.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Add support for O_TMPFILE

O_TMPFILE was added in Linux 3.11. We wrap this in an #ifdef as this was
only added in glibc 2.19.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Wrap O_PATH in an #ifdef

O_PATH was added in glibc 2.14. RHEL 6 for example is based on 2.12.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>