lib: fix MIN/MAX macros to not double-eval

cf. https://gcc.gnu.org/onlinedocs/gcc/Typeof.html
(Works on all compilers on Quagga's compiler support list in
doc/overview.texi)

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Tested-by: NetDEF CI System <cisystem@netdef.org>
Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>
1 file changed